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Evaporites are water-soluble mineral
Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
 sediments
Sedimentary rock

Sedimentary rock is one of the three main Rock types . Sedimentary rock is formed by deposition and consolidation of mineral and organic material and from precipitation of minerals from solution....
 that result from the evaporation
Evaporation

Evaporation is the slow vaporization of a liquid and the reverse of condensation. A type of phase transition, it is the process by which molecules in a liquid State of matter spontaneously become gaseous ....
 of bodies of surficial water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
. Evaporites are considered sedimentary rocks.

ough all water bodies on the surface and in aquifers contain dissolved salts, the water must evaporate into the atmosphere for the minerals to precipitate. For this to happen the water body must enter a restricted environment where water input into this environment remains below the net rate of evaporation.






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Evaporites are water-soluble mineral
Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
 sediments
Sedimentary rock

Sedimentary rock is one of the three main Rock types . Sedimentary rock is formed by deposition and consolidation of mineral and organic material and from precipitation of minerals from solution....
 that result from the evaporation
Evaporation

Evaporation is the slow vaporization of a liquid and the reverse of condensation. A type of phase transition, it is the process by which molecules in a liquid State of matter spontaneously become gaseous ....
 of bodies of surficial water
Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
. Evaporites are considered sedimentary rocks.

Formation of evaporite rocks

Although all water bodies on the surface and in aquifers contain dissolved salts, the water must evaporate into the atmosphere for the minerals to precipitate. For this to happen the water body must enter a restricted environment where water input into this environment remains below the net rate of evaporation. This is usually an arid
Arid

A region is said to be arid when it is characterized by a severe lack of available water, to the extent of hindering or even preventing the Individual growth and Morphogenesis of plant and animal life....
 environment with a small basin fed by a limited input of water. When evaporation occurs, the remaining water is enriched in salts, and they precipitate when the water becomes oversaturated.

Evaporite depositional environments

Evaporite depositional environments
Sedimentary depositional environment

In geology, sedimentary depositional environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock record....
 which meet the above conditions include;
  • Graben
    Graben

    A graben is a depression block of land bordered by parallel Fault s. Graben is German language for ditch.A graben is the result of a block of land being downthrown producing a valley with a distinct Escarpment on each side....
     areas and half-grabens within continental rift environments fed by limited riverine drainage, usually in subtropical or tropical environments
    • Example environments at the present which match this is the Denakil Depression, Ethiopia
      Ethiopia

      Ethiopia , officially the Federal Democratic Republic of Ethiopia, is a landlocked country situated in the Horn of Africa. Ethiopia is bordered by Eritrea to the north, Sudan to the west, Kenya to the south, Somalia to the east and Djibouti to the northeast....
      ; Death Valley
      Death Valley

      Death Valley is a desert located in the southwestern United States. It is the lowest, driest, and hottest location in North America. Badwater, a depression located within Death Valley, is the specific location of the lowest elevation in North America at 85.5 meter below sea level....
      , California
      California

      California is a U.S. state on the West Coast of the United States of the United States, along the Pacific Ocean. It is bordered by Oregon to the north, Nevada to the east, Arizona to the southeast, and to the south the Mexico state of Baja California....
  • Graben environments in oceanic rift environments fed by limited oceanic input, leading to eventual isolation and evaporation
    • Examples include the Red Sea, and the Dead Sea
      Dead Sea

      For the Brian Keene book of the same name, see Dead Sea The Dead Sea is a salt lake between Israel and the West Bank to the west, and Jordan to the east....
       in Jordan
      Jordan

      Jordan , officially the Hashemite Kingdom of Jordan, is an Arab country in Southwest Asia spanning the southern part of the Syrian Desert down to the Gulf of Aqaba....
       and Israel
      Israel

      Israel officially the State of Israel , is a country in the Middle East located on the eastern shore of the Mediterranean Sea. It borders Lebanon in the north, Syria in the northeast, Jordan in the east, and Egypt on the southwest, and contains geographically diverse features within its relatively small area....
  • Internal drainage basins in arid to semi-arid temperate to tropical environments fed by ephemeral drainage
    • Example environments at the present include the Simpson Desert
      Simpson Desert

      The Simpson Desert occupies approximately 176,500 square kilometres of central Australia. It is located within, and near the common boundaries of the Northern Territory, South Australia and Queensland states of Australia....
      , Western Australia
      Western Australia

      Western Australia is a States and territories of Australia occupying the entire western third of the Australia . The nation's largest state and the second largest subnational entity in the world, it has 2.1 million inhabitants , 85% of whom live in the south-west corner of the state....
      , the Great Salt Lake
      Great Salt Lake

      Great Salt Lake, located in the northern part of the U.S. state of Utah, is the largest salt lake in the western hemisphere, the fourth-largest Endorheic in the world, and the 37th largest lake on Earth....
       in Utah
      Utah

      The State of Utah is a western United States U.S. state of the United States. It was the List of U.S. states by date of statehood admitted to the United States on January 4, 1896....
  • Non-basin areas fed exclusively by groundwater seepage from artesian waters
    • Example environments include the seep-mounds of the Victoria Desert, fed by the Great Artesian Basin
      Great Artesian Basin

      The Great Artesian Basin provides the only reliable source of water through much of inland Australia. The basin is the largest and deepest Artesian aquifer in the world, covering a total of ....
      , Australia
      Australia

      Australia, officially the Commonwealth of Australia, is a country in the southern hemisphere comprising the Australia of the world's smallest continent, the major island of Tasmania, and numerous list of islands of Australia in the Indian Ocean and Pacific Oceans....
  • Restricted coastal plains in regressive sea environments
    • Examples include the sabkha
      Sabkha

      File:Sebkhat El Melah,1999.jpgFile:Sebkhat El Melah,1987.jpgSabkha is a transliteration of the Arabic language word for a salt flat. Sabkhas are supratidal, forming along arid coastlines and are characterized by evaporite-carbonate deposits with some siliciclastics....
       deposits of Iran, Saudi Arabia and the Red Sea
  • Drainage basins feeding into extremely arid environments
    • Examples include the Chilean deserts, certain parts of the Sahara
      Sahara

      The Sahara is the world's largest hot desert. At over 9,000,000 square kilometers , it covers most of Northern Africa, making it almost as large as the United States or the continent of Europe....
       and the Namib


Evaporitic formations

Evaporite formations need not be composed entirely of halite salt. In fact, most evaporite formations do not contain more than a few percent of evaporite minerals, the remainder being composed of the more typical detrital clastic rocks and carbonates.

For a formation to be recognised as evaporitic it may simply require recognition of halite pseudomorph
Pseudomorph

In mineralogy, a pseudomorph is a mineral or mineral compound that appears in an untypical form , resulting from a substitution process in which the appearance and dimensions remain constant, but the original mineral is replaced by another....
s, sequences composed of some proportion of evaporite minerals, and recognition of mud crack textures or other textures
Rock microstructure

Rock microstructure includes the Texture of a rock and the small scale rock structures. The words "texture" and "microstructure" are interchangeable, with the latter preferred in modern geological literature....
.

Economic importance of evaporites

Evaporites are important economically because of their mineralogy, their physical properties in-situ and their behaviour within the subsurface.

Evaporite minerals, especially nitrate minerals, are economically important in Peru and Chile. Nitrate minerals are often mined for use in the production on fertilizer
Fertilizer

Fertilizers are chemical compounds given to plants to promote growth; they are usually applied either through the soil, for uptake by plant roots, or by foliar feeding, for uptake through leaves....
 and explosives.

Thick halite deposits are expected to become an important location for the disposal of nuclear waste because of their geologic stability, predictable engineering and physical behaviour and imperviousness to groundwater.

Halite formations are famous for their ability to form diapirs which produce ideal locations for trapping petroleum
Petroleum

Petroleum or crude oil is a naturally occurring, flammable liquid found in rock formations in the Earth consisting of a complex mixture of hydrocarbons of various molecular weights, plus other organic compounds....
 deposits.

Major groups of evaporite minerals

  • Halides: halite
    Halite

    Halite is the mineral form of sodium chloride, sodiumchlorine, commonly known as rock salt. Halite forms Cubic crystals. The mineral is typically colorless to yellow, but may also be light blue, dark blue, and pink depending on the amount and type of impurities....
    , sylvite
    Sylvite

    Sylvite is potassium chloride in natural mineral form. It forms crystals in the Cubic system very similar to normal rock salt, halite . . Sylvite has a salty taste with a distinct bitterness....
     (KCl), and fluorite
    Fluorite

    Fluorite is a mineral composed of calcium fluoride, CalciumFluorine. It is an Cubic mineral with a cubic habit, though octahedral and more complex isometric forms are not uncommon....
  • Sulfates: such as gypsum
    Gypsum

    Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula calciumsulfuroxygen4?2water....
    , barite
    Barite

    Baryte is a mineral consisting of barium sulfate. It is generally white or colorless, and is the main source of barium. Barite is the unofficial American spelling....
    , and anhydrite
    Anhydrite

    Anhydrite is a mineral - anhydrous calcium sulfate, CaSO4. It is in the orthorhombic crystal system, with three directions of perfect cleavage parallel to the three planes of symmetry....
  • Nitrates: nitratite (soda niter) and niter
  • Borates: typically found in arid-salt-lake deposits plentiful in the southwestern US
    United States

    The United States of America is a Federal government constitutional republic comprising U.S. state and a federal district. The country is situated mostly in central North America, where its Contiguous United States and Washington, D.C., the Capital districts and territories, lie between the Pacific Ocean and Atlantic Oceans, Borders of the U...
    . A common borate is borax
    Borax

    Borax, also known as sodium borate, sodium tetraborate, or disodium tetraborate, is an important boron compound, a mineral, and a salt of boric acid....
    , which has been used in soap
    SOAP

    SOAP, originally defined as Simple Object Access Protocol, is a protocol specification for exchanging structured information in the implementation of Web Services in computer networks....
    s as a surfactant
    Surfactant

    Surfactants are wetting agents that lower the surface tension of a liquid, allowing easier spreading, and lower the interfacial tension between two liquids....
    .
  • Carbonates: such as trona
    Trona

    Trona ; sodium3hydrogen2·2water) is an evaporite mineral. It is Mining as the primary source of sodium carbonate in the United States, where it has replaced the Solvay process used in most of the rest of the world for sodium carbonate production....
    , formed in inland brine lakes.


Evaporite minerals start to precipitate
Precipitation (chemistry)

Precipitation is the formation of a solid in a solution during a chemical reaction. When the reaction occurs, the solid formed is called the precipitate, and the liquid remaining above the solid is called the supernate....
 when their concentration in water reaches such a level that they can no longer exist as solutes.

The minerals precipitate out of solution in the reverse order of their solubilities, such that the order of precipitation from sea water is
  1. Calcite
    Calcite

    Calcite is a Carbonate minerals and the most stable Polymorphism of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite....
     (CaCO3) and dolomite
    Dolomite

    Dolomite is the name of a sedimentary carbonate rock and a mineral, both composed of calcium magnesium carbonate calciummagnesium2 found in crystals....
     (CaMg(CO3)2)
  2. Gypsum (CaSO4-2H2O) and anhydrite (CaSO4).
  3. Halite (i.e. common salt, NaCl)
  4. Potassium
    Potassium

    Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
     and magnesium
    Magnesium

    Magnesium is a chemical element with the symbol Mg, atomic number 12, atomic weight 24.3050 and common oxidation number +2.Magnesium, an alkaline earth metal, is the ninth most abundance of the chemical elements in the universe by mass....
     salts


The abundance of rocks formed by seawater precipitation is in the same order as the precipitation given above. Thus, limestone
Limestone

File:Limestone Formation In Waitomo.jpgLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geology record....
 (calcite
Calcite

Calcite is a Carbonate minerals and the most stable Polymorphism of calcium carbonate . The other polymorphs are the minerals aragonite and vaterite....
) and dolomite
Dolomite

Dolomite is the name of a sedimentary carbonate rock and a mineral, both composed of calcium magnesium carbonate calciummagnesium2 found in crystals....
 are more common than gypsum
Gypsum

Gypsum is a very soft mineral composed of calcium sulfate dihydrate, with the chemical formula calciumsulfuroxygen4?2water....
, which is more common than halite
Halite

Halite is the mineral form of sodium chloride, sodiumchlorine, commonly known as rock salt. Halite forms Cubic crystals. The mineral is typically colorless to yellow, but may also be light blue, dark blue, and pink depending on the amount and type of impurities....
, which is more common than potassium
Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
 and magnesium
Magnesium

Magnesium is a chemical element with the symbol Mg, atomic number 12, atomic weight 24.3050 and common oxidation number +2.Magnesium, an alkaline earth metal, is the ninth most abundance of the chemical elements in the universe by mass....
 salts.

Evaporites can also be easily recrystallized
Recrystallization

Recrystallization is a physical process that has meanings in chemistry, metallurgy and geology....
 in laboratories in order to investigate the conditions and characteristics of their formation.

See also

  • List of minerals
    List of minerals

    This is a List of minerals for which there are Wikipedia articles. Mineral variety names and mineraloids are to be listed after the valid minerals for each letter....
  • List of rock types
  • Salt dome
    Salt dome

    A salt dome is a type of Dome formed when a thick bed of evaporite minerals found at depth intrudes vertically into surrounding rock Stratum, forming a diapir....
  • Diapir
    Diapir

    A diapir is a type of intrusion in which a more mobile and ductily-deformable material is forced into brittle overlying rocks. Depending on the tectonic environment, diapirs can range from idealized mushroom-shaped Rayleigh-Taylor instability-type structures in regions with low tectonic stress such as in the Gulf of Mexico to narrow dike...
  • Tectonic rifts
  • Graben
    Graben

    A graben is a depression block of land bordered by parallel Fault s. Graben is German language for ditch.A graben is the result of a block of land being downthrown producing a valley with a distinct Escarpment on each side....