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clay is one the best. it makes it good for people.

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-{{otheruses}}
-[[Image:Gay head cliffs MV.JPG|right|thumb|The Gay Head cliffs in [[Martha's Vineyard]] are made almost entirely of clay.]]
-'''Clay''' is a naturally occurring material composed primarily of fine-grained [[mineral]]s, which show [[plasticity (physics)|plasticity]] through a variable range of [[water content]], and which can be hardened when dried and/or fired. Clay [[deposit (geology)|deposits]] are mostly composed of [[clay minerals]] ([[Silicate minerals#Phyllosilicates|phyllosilicate minerals]]), minerals which impart plasticity and harden when fired and/or dried, and variable amounts of water trapped in the mineral structure by [[chemical polarity|polar attraction]]. [[Organic material]]s which do not impart plasticity may also be a part of clay deposits.<ref name="guggenheim">{{harvnb|Guggenheim|Martin|1995|pp=255–256}}</ref>
-Clay minerals are typically formed over long periods of time by the gradual chemical [[weathering]] of rocks (usually silicate-bearing) by low concentrations of [[carbonic acid]] and other diluted [[solvents]]. These solvents (usually acidic) migrate through the weathering rock after [[leaching]] through upper weathered layers. In addition to the weathering process, some clay minerals are formed by [[hydrothermal]] activity. Clay deposits may be formed in place as residual deposits, but thick deposits usually are formed as the result of a secondary [[sedimentary]] deposition process after they have been eroded and transported from their original location of formation. Clay deposits are typically associated with very low energy depositional environments such as large lake and marine deposits.
-== Definition ==
-Clays are distinguished from other fine-grained soils by various differences in composition. [[Silt]]s, which are fine-grained soils which do not include clay minerals, tend to have larger particle sizes than clays, but there is some overlap in both particle size and other physical properties, and there are many naturally occurring deposits which include both silts and clays. The distinction between silt and clay varies by discipline. [[Geologist]]s and [[soil scientist]]s usually consider the separation to occur at a particle size of 2 [[Micrometre|µm]] (clays being finer than silts), [[sedimentologist]]s often use 4-5 μm, and [[colloid]] [[chemist]]s use 1 μm.<ref name="guggenheim"/> [[Geotechnical engineering|Geotechnical engineers]] distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils' [[Atterberg Limits]].  ISO 14688 grades clay particles as being smaller than 0.063 mm, and silts larger.
-[[Image:Clay-ss-2005.jpg|thumb|[[Quaternary]] clay in [[Estonia]].]]Primary clays, also known as kaolins are located at the site of formation. Secondary clay deposits have been moved by [[erosion]] and water from its primary location<ref>[http://pubs.usgs.gov/info/clays/ Environmental Characteristics of Clays and Clay Mineral Deposits<!-- Bot generated title -->]</ref>.
-===Grouping===
-Depending upon academic source, there are three or four main groups of clays: [[kaolin]]ite, [[montmorillonite]]-[[smectite]], [[illite]], and [[Chlorite group|chlorite]]. Chlorites are not always considered a clay, sometimes being classified as a separate group within the [[phyllosilicate]]s. There are approximately thirty different types of "pure" clays in these categories, but most "natural" clays are mixtures of these different types, along with other weathered minerals.
-[[Varve]] (or ''varved clay'') is clay with visible annual layers, formed by seasonal differences in [[erosion]] and organic content. This type of [[deposit]] is common in former [[glacial lake]]s.
-[[Quick clay]] is a unique type of [[marine clay]] indigenous to the glaciated terrains of [[Norway]], [[Canada]] and [[Sweden]]. It is a highly sensitive clay, prone to [[liquefaction]], which has been involved in several deadly [[landslides]].
-==Historical and modern uses==
-[[Image:Clay In A Construction Site.jpg|thumb|right|Clay layers in a construction site. Dry clay is normally much more stable than sand with regards to excavations.]]
-Clays exhibit [[Plasticity (physics)|plasticity]] when mixed with water in certain proportions. When dry, clay becomes firm and when [[Pottery firing|fired]] in a [[kiln]], permanent physical and chemical reactions occur which, amongst other changes, causes the clay to be converted into a [[ceramic]] material. It is because of these properties that clay is used for making [[pottery]] items, both practical and decorative. Different types of clay, when used with different [[mineral]]s and firing conditions, are used to produce [[earthenware]], [[stoneware]] and [[porcelain]]. Early humans discovered the useful properties of clay in prehistoric times, and one of the earliest artifacts ever uncovered is a drinking vessel made of sun-dried clay.{{Fact|date=May 2008}} Depending on the content of the soil, clay can appear in various colors, from a dull gray to a deep orange-red.
-Clay tablets were used as the first writing medium, inscribed with [[cuneiform]] script through the use of a blunt [[Reed (plant)|reed]] called a [[stylus]].
-Clays [[sintering|sintered]] in fire were the first form of [[ceramic]]. [[Brick]]s, cooking pots, art objects, [[dishware]] and even musical instruments such as the [[ocarina]] can all be shaped from clay before being fired. Clay is also used in many industrial processes, such as [[paper]] making, [[cement]] production and chemical [[filter (chemistry)|filter]]ing.  Clay is also often used in the manufacture of pipes for smoking [[tobacco]].
-Clay, being relatively [[Permeability (fluid)|impermeable]] to water, is also used where natural seals are needed, such as in the cores of [[dam]]s, or as a barrier in [[landfill]]s against toxic seepage ('lining' the landfill, preferably in combination with [[geotextile]]s).<ref>''[http://www2.widener.edu/~sxw0004/abstract34.html Preliminary evaluation of a compacted bentonite / sand mixture as a landfill liner material'' (Abstract)] - Koçkar, Mustafa K.; Akgün, Haluk; Aktürk, Özgür; Department of Geological Engineering, [[Middle East Technical University]], [[Ankara]], [[Turkey]]</ref>
-Recent studies have been carried out to investigate clay's [[adsorption]] capacities in various applications, such as the removal of [[heavy metals]] from waste water and air purification.
-===Medical===
-A recent article in ''The Journal of Antimicrobial Chemotherapy'' found that certain iron-rich clay was effective in killing bacteria.<ref>[http://jac.oxfordjournals.org/cgi/content/abstract/61/2/353 Broad-spectrum in vitro antibacterial activities of clay minerals against antibiotic-susceptible and antibiotic-resistant bacterial pathogens]</ref>
-==See also==
-{{wiktionary}}
-<table><tr><td valign=top>
-* [[Bentonite]]
-* [[Ceramic]]
-* [[Clay (industrial plasticine)]]
-* [[Clay animation]]
-* [[Clay court]]
-* [[Clay minerals]]
-* [[Clay pit]]
-* [[Geophagy]] (eating of soils, including eating of clay)
-* [[Expansive clay]]
-* [[Graham Cairns-Smith]], proposed the 'clay theory' of [[abiogenesis]]
-<td valign=top>
-* [[List of minerals]]
-* [[London Clay]]
-* [[Modelling clay]]
-* [[Paperclay]]
-* [[Particle size]]
-* [[Plasticine]]
-* [[Pottery]]
-* [[Vertisol]]
-</tr></td></table>
-==Footnotes==
-{{reflist}}
-==References==
-*{{Citation
-  | last =Guggenheim
-  | first =Stephen
-  | last2 =Martin
-  | first2 =R. T.
-  | title =Definition of clay and clay mineral: Journal report of the AIPEA nomenclature and CMS nomenclature committees
-  | journal =Clays and Clay Minerals
-  | volume =43
-  | pages =255–256
-  | year =1995
-  | url =http://www.clays.org/journal/archive/volume%2043/43-2-255.pdf
-}}
-* [http://www.minsocam.org/msa/collectors_corner/arc/nomenclaturecl1.htm Clay mineral nomenclature] ''American Mineralogist''.
-*Ehlers, Ernest G. and Blatt, Harvey (1982).  'Petrology, Igneous, Sedimentary, and Metamorphic' [[San Francisco]]: W.H. Freeman and Company.  ISBN 0-7167-1279-2.
-*Hillier S. (2003) Clay Mineralogy. pp 139-142 In: Middleton G.V., Church M.J., Coniglio M., Hardie L.A. and Longstaffe F.J.(Editors) Encyclopedia of sediments and sedimentary rocks. Kluwer Academic Publishers, Dordrecht.
-==External links==
-{{commonscat|Clay}}
-*[http://www.minersoc.org/pages/groups/cmg/cmg.html The Clay Minerals Group of the Mineralogical Society]
-*[http://www.stoke.gov.uk/ccm/museums/museum/2006/gladstone-pottery-museum/information-sheets/clay-in-north-staffordshire.en Historical information about the clays of North Staffordshire, UK]
-* [http://www.stoke.gov.uk/ccm/museums/museum/2006/gladstone-pottery-museum/information-sheets/clays-used-in-the-pottery-industry.en Information about clays used in the UK pottery industry]
-<!-- * [http://www.who.int/entity/ipcs/publications/ehc/ehc231.pdf ''Bentonite, kaolin, and selected clay minerals''] ([[PDF]]) (Volume 231, ''Environmental Health Criteria'', [[World Health Organisation]], 2005) -->
-{{Geotechnical engineering|state=collapsed}}
-[[Category:Ceramics]]
-[[Category:Ceramic materials]]
-[[Category:Sculpture materials]]
-[[Category:Natural materials]]
-[[Category:Sedimentology]]
-[[Category:Sediments]]
-[[Category:Silicate minerals]]
-[[Category:Types of soil]]
-[[ar:طين]]
-[[an:Archila (sedimento)]]
-[[ay:Llink'i laq'a]]
-[[bs:Glina]]
-[[bg:Глина]]
-[[ca:Argila]]
-[[cv:Тăм]]
-[[cs:Jíl]]
-[[da:Ler]]
-[[de:Tonminerale]]
-[[et:Savi]]
-[[es:Arcilla]]
-[[eo:Argilo]]
-[[eu:Buztin]]
-[[fa:رس]]
-[[fr:Argile]]
-[[hr:Glina (tlo)]]
-[[id:Tanah liat]]
-[[it:Argilla]]
-[[he:חרסית]]
-[[lv:Māls]]
-[[lt:Molis (uoliena)]]
-[[hu:Agyag]]
-[[ms:Tanah liat]]
-[[nl:Klei]]
-[[ja:粘土]]
-[[no:Leire]]
-[[pl:Glina]]
-[[pt:Argila]]
-[[ru:Глина]]
-[[sq:Deltina]]
-[[scn:Argilla]]
-[[simple:Clay]]
-[[ss:Lubumba]]
-[[sk:Íl]]
-[[sr:Глина]]
-[[sh:Gline]]
-[[fi:Savi]]
 [[sv:Lera]]
 [[th:ดินเหนียว]]
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 [[bat-smg:Muolis]]
 [[zh:黏土]]
+ clay is one the best. it makes it good for people.