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Caliche Forest on San Miguel Island.

Caliche (/kəˈl/) is a sedimentary rock, a hardened natural cement of calcium carbonate that binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or semiarid regions, including in central and western Australia, in the Kalahari Desert, in the High Plains of the western USA, in the Sonoran Desert, Chihuahuan Desert and Mojave Desert of North America, and in Eastern Saudi Arabia at Al-Hasa. Caliche is also known as calcrete or kankar (in India). It belongs to the duricrusts. The term caliche is Spanish and is originally from the Latin calx, meaning lime.[1]

Caliche is generally light-colored, but can range from white to light pink to reddish-brown, depending on the impurities present. It generally occurs on or near the surface, but can be found in deeper subsoil deposits, as well. Layers vary from a few inches to feet thick, and multiple layers can exist in a single location. A caliche layer in a soil profile is sometimes called a K horizon.[2][3]

In northern Chile and Peru, caliche also refers to mineral deposits that include nitrate salts.[4][5] Caliche can also refer to various claylike deposits in Mexico and Colombia. In addition, it has been used to describe some forms of quartzite, bauxite, kaolinite, laterite, chalcedony, opal, and soda niter.



Caliche forms where annual precipitation is less than 65 centimeters (26 in) per year and the mean annual temperature exceeds 5 °C (41 °F). Higher rainfall leaches excess calcium completely from the soil, while in very arid climates, rainfall is inadequate to leach calcium at all and only thin surface layers of calcite are formed. Plant roots play an important role in caliche formation, by releasing large amounts of carbon dioxide into the A horizon of the soil. Carbon dioxide levels here can exceed 15 times normal atmospheric values. This allows calcium carbonate to dissolve as bicarbonate. Where rainfall is adequate but not excessive, the calcium bicarbonate is carried down into the B horizon. Here there is less biological activity, the carbon dioxide level is much lower, and the bicarbonate reverts to insoluble carbonate. A mixture of calcium carbonate and clay particles accumulates, first forming grains, then small clumps, then a discernible layer, and finally, a thicker, solid bed.[6] As the caliche layer forms, the layer gradually becomes deeper, and eventually moves into the parent material, which lies under the upper soil horizons.[citation needed]

However, caliche also forms in other ways. It can form when water rises through capillary action. In an arid region, rainwater sinks into the ground very quickly. Later, as the surface dries out, the water below the surface rises, carrying up dissolved minerals from lower layers. These precipitate as water evaporates and carbon dioxide is lost. This water movement forms a caliche that is close to the surface.[7] Caliche can also form on outcrops of porous rocks or in rock fissures where water is trapped and evaporates.[8] In general, caliche deposition is a slow process, requiring several thousand years,[3] but if enough moisture is present in an otherwise arid site, it can accumulate fast enough to block a drain pipe.[citation needed]

The depth of the caliche layer is sensitive to mean annual rainfall. When rainfall is around 35 centimeters (14 in) per year, the caliche layer will be as shallow as 25 centimeters (9.8 in). When rainfall is around 75 centimeters (30 in) per year, the caliche layer will be at a depth of around 125 centimeters (49 in). The caliche layer disappears complete in temperate climates if annual rainfall exceeds 100 centimeters (39 in).[9]

Examples of natural occurrence[edit]

Caliche — sedimentary rock, Ridgecrest, Kern County, California
Calcrete rubble was widely used for building construction in South Australia during the 19th century.



Economic uses[edit]

Building applications[edit]


Caliche berm surrounding a stock tank in Central Texas

When mixed with small amounts of either pozzolan or Portland cement, caliche can also be used as a building material that exceeds building code requirements for unfired masonry materials. For example, caliche was used to build some of the Mayan buildings in the Yucatán Peninsula in Mexico. A dormitory in Ingram, Texas, and a demonstration building in Carrizo Springs, Texas, for the United States Department of Energy were also built using caliche as part of studies by the Center for Maximum Potential Building Systems.

In many areas, caliche is also used for road construction, either as a surfacing material, or more commonly, as base material. It is one of the most common road materials used in Southern Africa. Caliche is widely used as a base material when it is locally available and cheap. However, it does not hold up to moisture (rain), and is never used if a hard-rock base material, such as limestone, is available.

Sugar refining[edit]


Chilean caliche[edit]

In the Atacama Desert in northern Chile, vast deposits of a mixture, also referred to as caliche, are composed of gypsum, sodium chloride and other salts, and sand, associated to salitre ("Chile saltpeter"). Salitre, in turn, is a composite of sodium nitrate (NaNO3) and potassium nitrate (KNO3). Salitre was an important source of export revenue for Chile until World War I, when Europe began to produce both nitrates industrially in large quantities.


Caliche and agriculture[edit]

Problems caused by caliche[edit]


A caliche layer with the presence of calcium carbonates indicates alkaline or high-pH conditions.

See also[edit]


  1. ^ Breazeale, J.F.; Smith, H.V. (15 April 1930). "Caliche in Arizona". Agricultural Experiment Station Bulletin. University of Arizona. 131: 419.
  2. ^ Gile, L. H.; Peterson, F. F.; Grossman, R. B. (February 1965). "The K Horizon". Soil Science. 99 (2): 74–82. Bibcode:1965SoilS..99...74G. doi:10.1097/00010694-196502000-00002. S2CID 129247211.
  3. ^ a b Allaby, Michael, ed. (2013). "Caliche". A dictionary of geology and earth sciences (Fourth ed.). Oxford: Oxford University Press. ISBN 9780199653065.
  4. ^ Chong et al. 2007, p. 211.
  5. ^ A Most Damnable Invention: Dynamite, Nitrates, and the Making of the Modern World, Stephen R. Bown, Macmillan, 2005, ISBN 0-312-32913-X, p. 157.
  6. ^ Blatt, Harvey; Middleton, Gerard; Murray, Raymond (1980). Origin of sedimentary rocks (2d ed.). Englewood Cliffs, N.J.: Prentice-Hall. pp. 273–275. ISBN 0136427103.
  7. ^ Blatt, Middleton & Murray 1980, pp. 274–275.
  8. ^ Breazeale & Smith 1930, pp. 420, 428–429.
  9. ^ Blatt, Middleton & Murray 1980, p. 274.

Further reading[edit]

  • Chong Diaz, Guillermo; Gajardo Cubillos, Aníbal; Hartley, Adrian J.; Moreno, Teresa (2006). "7. Industrial minerals and rocks". In Moreno, Teresa; Gibbons, Wes (eds.). Geology of Chile. Geological Society of London. pp. 21–114. ISBN 9781862392199.

External links[edit]