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Sand "dunes in the "Idehan Ubari, Libya.
Close-up (1×1 cm) of sand from the "Gobi Desert, Mongolia.

Sand is a naturally occurring "granular material composed of finely divided "rock and "mineral particles. It is defined by size, being finer than "gravel and coarser than "silt. Sand can also refer to a "textural class of soil or soil type; i.e., a soil containing more than 85 percent sand-sized particles by mass.[1]

The composition of sand varies, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-"tropical "coastal settings is "silica (silicon dioxide, or SiO2), usually in the form of "quartz. The second most common type of sand is "calcium carbonate, for example, "aragonite, which has mostly been created, over the past half billion years, by various forms of life, like "coral and "shellfish. For example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like the "Caribbean.

Sand is a non-renewable resource over human timescales, and sand suitable for making concrete is in high demand.[2]



Heavy minerals (dark) in a quartz beach sand ("Chennai, India).
Sand from "Coral Pink Sand Dunes State Park, "Utah. These are grains of "quartz with a "hematite coating providing the orange color.
Sand from "Pismo Beach, California. Components are primarily "quartz, "chert, "igneous rock and shell fragments.

The exact definition of sand varies. The scientific "Unified Soil Classification System used in engineering and geology corresponds to US Standard Sieves,[3] and defines sand as particles with a diameter of between 0.074 and 4.75 millimeters. By another definition, in terms of "particle size as used by "geologists, sand particles range in diameter from 0.0625 mm (or ​116 mm) to 2 mm. An individual particle in this range size is termed a sand grain. Sand grains are between "gravel (with particles ranging from 2 mm up to 64 mm by the latter system, and from 4.75 mm up to 75 mm in the former) and "silt (particles smaller than 0.0625 mm down to 0.004 mm). The size specification between sand and gravel has remained constant for more than a century, but particle diameters as small as 0.02 mm were considered sand under the "Albert Atterberg standard in use during the early 20th century. A 1953 engineering standard published by the "American Association of State Highway and Transportation Officials set the minimum sand size at 0.074 mm. A 1938 specification of the "United States Department of Agriculture was 0.05 mm.[4] Sand feels gritty when rubbed between the fingers. "Silt, by comparison, feels like "flour).

"ISO 14688 grades sands as fine, medium, and coarse with ranges 0.063 mm to 0.2 mm to 0.63 mm to 2.0 mm. In the United States, sand is commonly divided into five sub-categories based on size: very fine sand (​116 – ​18 mm diameter), fine sand (​18 mm – ​14 mm), medium sand (​14 mm – ​12 mm), coarse sand (​12 mm – 1 mm), and very coarse sand (1 mm – 2 mm). These sizes are based on the "Krumbein phi scale, where size in Φ = -log2D; D being the particle size in mm. On this scale, for sand the value of Φ varies from −1 to +4, with the divisions between sub-categories at whole numbers.

Close up of black volcanic sand from Perissa, "Santorini, Greece

The most common constituent of sand, in inland continental settings and non-tropical coastal settings, is "silica (silicon dioxide, or SiO2), usually in the form of "quartz, which, because of its chemical inertness and considerable hardness, is the most common "mineral resistant to "weathering.

The composition of mineral sand is highly variable, depending on the local rock sources and conditions. The bright "white sands found in tropical and subtropical coastal settings are eroded "limestone and may contain "coral and "shell fragments in addition to other "organic or organically derived fragmental material, suggesting sand formation depends on living organisms, too.[5] The "gypsum sand dunes of the "White Sands National Monument in "New Mexico are famous for their bright, white color. "Arkose is a sand or "sandstone with considerable "feldspar content, derived from "weathering and "erosion of a (usually nearby) "granitic rock outcrop. Some sands contain "magnetite, "chlorite, "glauconite or "gypsum. Sands rich in "magnetite are dark to black in color, as are sands derived from volcanic "basalts and "obsidian. "Chlorite-"glauconite bearing sands are typically green in color, as are sands derived from "basaltic ("lava) with a high "olivine content. Many sands, especially those found extensively in "Southern Europe, have "iron impurities within the quartz "crystals of the sand, giving a deep yellow color. Sand deposits in some areas contain "garnets and other resistant minerals, including some small "gemstones.


An "electron micrograph showing grains of sand
Pitted sand grains from the Western Desert, Egypt. Pitting is a consequence of wind transportation.

The study of individual grains can reveal much historical information as to the origin and kind of transport of the grain.[6] "Quartz sand that is recently weathered from "granite or "gneiss quartz crystals will be angular. It is called "grus in geology or sharp sand in the building trade where it is preferred for concrete, and in gardening where it is used as a soil amendment to loosen clay soils. Sand that is transported long distances by water or wind will be rounded, with characteristic abrasion patterns on the grain surface. Desert sand is typically rounded.

People who collect sand as a hobby are known as "arenophiles. Organisms that thrive in sandy environments are psammophiles.[7]


Sand sorting tower at a "gravel pit.

Resources and environmental concerns[edit]

Only some sands are suitable for the construction industry, for example for making "concrete. Because of the growth of population and of cities and the consequent construction activity there is a huge demand for these special kinds of sand, and natural sources are running low. In 2012 French director "Denis Delestrac made a documentary called "Sand Wars" about the impact of the lack of construction sand. It shows the ecological and economic effects of both legal and illegal trade in construction sand.[10][11][12]

Sand's many uses require a significant "dredging industry, raising environmental concerns over fish depletion, landslides, and flooding.[13] Countries such as China, Indonesia, Malaysia and Cambodia ban sand exports, citing these issues as a major factor.[14] It is estimated that the annual consumption of sand and gravel is 40 billion tons and sand is a US$70 billion global industry.[15]


While sand is generally non-toxic, sand-using activities such as "sandblasting require precautions. Bags of silica sand used for sandblasting now carry labels warning the user to wear respiratory protection to avoid breathing the resulting fine silica "dust. "Safety data sheets for silica sand state that "excessive inhalation of crystalline silica is a serious health concern".[16]

In areas of high "pore water pressure, sand and salt water can form "quicksand, which is a "colloid "hydrogel that behaves like a liquid. Quicksand produces a considerable barrier to escape for creatures caught within, who often die from exposure (not from submersion) as a result.

See also[edit]


  1. ^ Glossary of terms in soil science (PDF). Ottawa: Agriculture Canada. 1976. p. 35. "ISBN "0662015339. 
  2. ^ Constable, Harriet (3 September 2017). "How the demand for sand is killing rivers". BBC News Magazine. Retrieved 9 September 2017. 
  3. ^ Unified Soil Classification System
  4. ^ Urquhart, Leonard Church, "Civil Engineering Handbook" McGraw-Hill Book Company (1959) p. 8-2
  5. ^ Seaweed also plays a role in the formation of sand. Susanscott.net (1 March 2002). Retrieved on 24 November 2011.
  6. ^ Krinsley, D.H., Smalley, I.J. 1972. Sand. American Scientist 60, 286-291
  7. ^ "Psammophile". Merriam-Webster.com. Retrieved 27 January 2016. 
  8. ^ "Importing Sand, Glass May Help Restore Beaches". NPR.org. 17 July 2007. 
  9. ^ Yong, Syed E. Hasan, Benedetto De Vivo, Bernhard Grasemann, Kurt Stüwe, Jan Lastovicka, Syed M. Hasan, Chen (2011-12-05). ENVIRONMENTAL AND ENGINEERING GEOLOGY -Volume III. EOLSS Publications. "ISBN "9781848263574. 
  10. ^ See Sand Wars teaser here.
  11. ^ "Simon Ings (26 April 2014). "The story of climate change gets star treatment". "New Scientist: 28–9. 
  12. ^ Strände in Gefahr? Arte Future, last updated 23 April 2014
  13. ^ Torres, Aurora; et al. (8 September 2017). "The world is facing a global sand crisis". The Conversation. Retrieved 9 September 2017. 
  14. ^ "The hourglass effect". The Economist. 8 October 2009. Retrieved 14 October 2009. 
  15. ^ Beiser, Vince (26 March 2015). "The Deadly Global War for Sand". Wired. Retrieved 26 March 2015. 
  16. ^ Silica sand MSDS Archived 11 March 2006 at the "Wayback Machine.. Simplot (13 March 2011). Retrieved on 24 November 2011.

External links[edit]

"" Media related to Sand at Wikimedia Commons

Sand Mining Side Effects
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