View source for Gravel

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[[Image:Gravel on a beach in Thirasia, Santorini, Greece.jpg|thumb|right|250px|Gravel (largest fragment in this photo is about 4 cm).]]
[[Image:Gravel1.jpg|thumb|right|250px|A gravel road in [[Terre Haute, Indiana]].]]
[[Image:gravel small.jpg|right|frame|Gravel being unloaded from a [[barge]]]]

'''Gravel''' is rock that is of a specific [[Particle size (grain size)|particle size]] range. Specifically, it is any loose [[rock (geology)|rock]] that is larger than 2&nbsp;mm (0.079&nbsp;in) in its smallest dimension (about 1/12 of an inch) and no more than {{convert|64|mm|in|abbr=on|lk=on}}. The next smaller size class in geology is [[sand]], which is >{{convert|0.0625|to|2|mm|in|4|abbr=on}} in size. The next larger size is [[cobble]], which is >{{convert|64|to|256|mm|in|1|abbr=on}}. Gravel can be sub-categorized into [[granule]] (>{{convert|2|to|4|mm|in|abbr=on|disp=/}}) and [[pebble]] (>{{convert|4|to|64|mm|in|abbr=on|disp=/}}). One cubic yard of gravel typically weighs about 3000 pounds (or a cubic meter is about 1,800 kilograms).

Gravel is an important commercial product, with a number of applications. Many [[road]]ways are [[pavement (roads)|surfaced]] with gravel, especially in [[rural]] areas where there is little [[traffic]]. Globally, far more roads are surfaced with gravel than with [[concrete]] or [[tarmac]]; [[Russia]] alone has over {{convert|400000|km|mi|abbr=on}} of gravel-surfaced roads. Both sand and small gravel are also important for the manufacture of [[concrete]].

==Geological formation==
Large gravel deposits are a common geological feature, being formed as a result of the [[weathering]] and [[erosion]] of rocks. The action of rivers and waves tends to pile up gravel in large accumulations. This can sometimes result in gravel becoming compacted and concreted into the sedimentary rock called [[Conglomerate (geology)|conglomerate]]. Where natural gravel deposits are insufficient for human purposes, gravel is often produced by quarrying and crushing hard-wearing rocks, such as sandstone, limestone, or basalt. Quarries where gravel is extracted are known as gravel pits. Southern [[England]] possesses particularly large concentrations of them due to the widespread deposition of gravel in the region during the [[Ice Age]]s.

===Modern production===
As of 2006, the [[United States]] is the world's leading producer and consumer of gravel.<ref>[http://minerals.usgs.gov/minerals/pubs/mcs/2006/mcs2006.pdf Mineral Commodity Summaries 2006] 2009</ref><ref>[http://www.indexmundi.com/en/commodities/minerals/silica/silica_t11.html Industrial Sand And Gravel (Silica): World Production, By Country] 2009</ref>

==Etymology==
The word comes from the [[French language|French]] ''gravelle'', meaning 'coarse sand'.

==Types==
[[Image:Gravel small stones.jpg|thumb|250px|Gravel with stones sized roughly between 5 and 15 millimeter.]]
[[Image:Kiesgrube.jpg|right|thumb|250px|Disused gravel pit in [[Lower Saxony]], [[Germany]]]]
Multiple types of gravel have been recognized, including:

* '''Bank gravel''': gravel intermixed with sand or clay.
* '''Bench gravel''': a bed of gravel located on the side of a valley above the present stream bottom, indicating the former location of the stream bed when it was at a higher level.
*'''Creek rock''': this is generally rounded, semi-polished stones, potentially of a wide range of types, that are dredged or scooped from [[river]] beds and creek beds. It is also often used as concrete aggregate and less often as a paving surface.
* '''Crushed rock''': [[Rock (geology)|rock]] that is mechanically broken into small pieces then sorted by filtering through different size [[mesh]].<!-- crushed rock redirects here -->
*'''Crushed stone''': this is generally [[limestone]] or [[dolomite]] that has been crushed and graded by screens to certain size classes. It is widely used in [[concrete]] and as a surfacing for roads and driveways, sometimes with [[tar]] applied over it. Crushed stone may also be made from [[granite]] and other rocks. A special type of limestone crushed stone is dense grade aggregate, or DGA, also known as crusher run. This is a mixed grade of mostly small crushed stone in a matrix of crushed limestone powder.
* '''Fine gravel''': gravel consisting of particles with a diameter of 2 to 4&nbsp;mm.
* '''Lag gravel''': a surface accumulation of coarse gravel produced by the removal of finer particles.
* '''Pay gravel''': also known as "pay dirt"; a nickname for gravel with a high concentration of gold and other precious metals. The metals are recovered through [[gold panning]].
* '''Pea gravel''': gravel that consists of small, rounded stones used in concrete surfaces. Also used for walkways, driveways and as a substrate in home aquariums.
* '''Piedmont gravel''': a coarse gravel carried down from high places by mountain streams and deposited on relatively flat ground, where the water runs more slowly.
* '''Plateau gravel''': a layer of gravel on a plateau or other region above the height at which stream-terrace gravel is usually found.
* '''[[River gravel|River run gravel]]''': naturally deposited gravel found in and next to rivers and streams.

==See also==

* [[Sediment]]
* [[Construction aggregate]]
* [[Clay]]
* [[Silt]]
* [[Sand]]
* [[Pebble]]
* [[Cobble]]
* [[Boulder]]

==References==
{{reflist}}

{{Geotechnical engineering|state=collapsed}}

[[Category:Sedimentology]]
[[Category:Granular materials]]
[[Category:Pavements]]
[[Category:Gardening aids]]
[[Category:Building supply]]
[[Category:Stone]]

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