Raffi at 03:58, 6 April 2007

2007-04-06T03:58:59Z

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[[Image:Sand patterns.jpg|thumb|300px|[[surface wave|Patterns]] in the sand]]

'''Sand''' is a [[granular material]] made up of fine rock particles. Sand is a naturally occurring, finely divided [[rock (geology)|rock]], comprising particles or granules ranging in size from 0.0625 (or {{Fraction|1|16}} mm) to 2 [[millimeter]]s. An individual particle in this range size is termed a '''sand grain'''. The next smaller size class in [[geology]] is [[silt]]: particles below 0.0625 mm down to 0.004 mm in size. The next larger size class above sand is [[gravel]], with particles ranging from 2 mm up to 64 mm (see [[particle size]] for standards in use). Sand feels gritty when rubbed between the fingers (silt feels like flour). Sand is commonly divided into five sub-categories based on size: very fine sand (1/16 - 1/8 mm), fine sand (1/8 mm - 1/4 mm), medium sand (1/4 mm - 1/2 mm), coarse sand (1/2 mm - 1 mm), and very coarse sand (1 mm - 2 mm). These sizes are based on the Φ sediment size scale, where size in Φ = -log base 2 of size in mm. On this scale sand is from Φ = -1 to 4, with the divisions between sub-categories at whole numbers.

== Constituents of sand ==
[[Image:Sand under electron microscope.jpg|thumb|right|300px|An electron micrograph showing grains of sand]]
[[Image:Volcanic sand (Perissa, Santorini, Greece).jpg|thumb|right|300px|Close up of black volcanic sand]]
The most common constituent of sand, in inland continental settings and non-[[tropical]] coastal settings, is [[silica]] (silicon dioxide, or SiO<sub>2</sub>), usually in the form of [[quartz]], which, because of its chemical inertness and considerable hardness, is resistant to [[weathering]]. The composition of sand varies according to local rock sources and conditions. The bright [[coral sand|white sands]] found in tropical and subtropical coastal settings are ground-up [[limestone]]. [[Arkose]] is a sand or [[sandstone]] with considerable [[feldspar]] content which is derived from the [[weathering]] and [[erosion]] of a (usually nearby) [[granite]]. Some locations have sands that contain [[magnetite]], [[chlorite group|chlorite]], [[glauconite]] or [[gypsum]]. Sands rich in magnetite are dark to black in color, as are sands derived from volcanic basalts. The chlorite-glauconite bearing sands are typically green in color, as are sands derived from [[basalt]]s ([[lava]]s) with a high [[olivine]] content. The gypsum sand dunes of the [[White Sands National Monument]] in [[New Mexico]] are famous for their bright, white color. Sand deposits in some areas contain [[garnet]]s and other resistant minerals, including some small [[gemstone]]s.

== Transport ==

Sand is transported by wind and water and deposited in the form of [[beach]]es, [[dune]]s, [[bar (landform)|sand spits]], [[bar (landform)|sand bars]], and the like.

== Study of sand ==
[[Image:Suesswasserstachelroche.jpg|thumb|right|250px|A [[stingray]] about to be buried in sand]]
Study of individual grains can reveal much historical information as to the origin, kind of transport, etc of the grain. Quartz sand that is recently weathered from [[granite]] or [[gneiss]] quartz crystals will be angular. It is called ''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 [[erosion]] transported long distances by water or wind will be rounded, with characteristic abrasion patterns on the grain surface.

==Uses of sand==
[[Image:Sanden ICE3.jpg|thumb|right|At 300 km/h, an [[Siemens Velaro|ICE 3]] (DB class 403) releases sand from several bogies to the rails.]]
[[Image:Sand sorting tower.jpg|thumb|right|Sand sorting tower at a gravel extraction pit.]]
*Sand is often a principal component of [[concrete]].

*[[Molding sand]], also known as [[foundry]] sand, is moistened or oiled and then shaped into molds for [[sand casting]]. This type of sand must be able to withstand high temperatures and pressure, allow gases to escape, have a uniform, small grain size and be non-reactiv
e with metals.

*Graded sand is used as an [[abrasive]] in [[sandblasting]] and is also used in [[media filter]]s for filtering [[water]].

*[[Brick]] [[manufacturing plant]]s use sand as an additive with a mixture of [[clay]] and other materials for manufacturing bricks.

*Sand is sometimes mixed with [[paint]] to create a [[Texture (crystalline)|texture]]d finish for walls and ceilings or a non-slip floor surface.

*Sandy [[soil]]s are ideal for certain crops such as [[watermelon]]s, [[peach]]es, and [[peanut]]s and are often preferred for intensive [[dairy farming]] because of their excellent drainage characteristics.

*Sand is used in [[Landscape engineering|landscaping]], it is added to make small hills and slopes (for example, constructing [[golf]] courses).

*It is the principal component in [[glass]] manufacturing.

*It is often transported to popular beaches where seasonal tides sweep its original sand into the sea.

*[[Sandbag]]s are used for protection against [[flood]]s and [[gun]] fire. They can be easily transported when empty, then filled with local sand.

*[[Sand castle]] building is a popular activity. There are competitive sand castle building competitions (See [[sand art and play]]).

*[[Sand animation]] is a type of [[performance art]] and a technique for creating [[animation|animated film]]s.

*[[Aquarium|Aquaria]] are often lined with sand instead of gravel. This is a low cost alternative which some believe is better than gravel.

*[[Railroads]] use sand to improve the traction of wheels on the rails.

==Hazards of sand==

While sand is generally harmless, one must take care with some activities involving sand such as [[sandblasting]]. Bags of silica sand now carry labels warning the user to wear respiratory protection and avoid breathing the fine silica dust. There have been a number of lawsuits in recent years where workers have developed [[silicosis]], a [[lung disease]] caused by inhalation of fine silica particles over long periods of time. [[Material safety data sheet]]s (MSDS) for silica sand state that "excessive inhalation of crystalline silica is a serious health concern" [http://www.simplot.com/industrial/silica/silica_msds.cfm].

In the natural environment, sand sometimes mixes with water or a similar liquid substance, to form [[quicksand]]. Quicksand, once dried, produces a considerable barrier to escape for creatures caught within, who often die from exposure as a result.

==See also==
{{wiktionary}}
{{commonscat|Sand}}
*[[Quicksand]]
*[[Dry quicksand]]
*[[Grain size]]
*[[Sandstone]]
*[[Dust storm|Sandstorm]]
*[[Singing sand]]
*[[White Sands National Monument]]

[[Category:Granular materials]]
[[Category:Pedology]]
[[Category:Sediments]]
[[Category:Sedimentology]]
[[Category:Geotechnical engineering]]

{{Link FA|nl}}

==External links==
* [http://www.bcgov.net/bftlib/beachsan.htm Beach Sand: What It Is, Where It Comes From and How It Gets Here -- Beaufort County Library]

Sand - Revision history

Raffi at 03:58, 6 April 2007