Editing Kaolinite

{{Short description|Phyllosilicate clay mineral}}
{{Redirect|Kaolin}}
{{See also|Aluminium silicate}}
{{Use dmy dates|date=June 2020}}
{{Infobox mineral
| name        = Kaolinite
| category    = [[Phyllosilicates]] <br />Kaolinite-[[serpentine group]]
| boxwidth    =
| image       = Kaolinite from Twiggs County in Georgia in USA.jpg
|imagesize=210px| alt         = 
| caption     =
| formula     = {{Chem2|Al2Si2O5(OH)4}}, or in oxide notation: {{Chem2|Al2O3*2SiO2*2H2O}}
| IMAsymbol   = Kln<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref>
| strunz      = 9.ED.05
| system      = [[Triclinic]]
| class       = Pedial (1) <br /><small>(same [[H-M symbol]])</small>
| symmetry    = ''P''1
| unit cell   = a = 5.13&nbsp;[[Ångstrom|Å]], b = 8.89&nbsp;Å <br />c = 7.25&nbsp;Å; α = 90° <br />β = 104.5°, γ = 89.8°; Z&nbsp;=&nbsp;2
| color       = White to cream, sometimes red, blue or brown tints from impurities and pale-yellow; also often stained various hues, tans and browns being common.
| habit       = Rarely as crystals, thin plates or stacked. More commonly as microscopic pseudohexagonal plates and clusters of plates, aggregated into compact, claylike masses.
| twinning    =
| cleavage    = Perfect on {001}
| fracture    =
| tenacity    = Flexible but inelastic
| mohs        = 2–2.5
| luster      = Pearly to dull earthy
| refractive  = n<sub>α</sub> = 1.553–1.565, <br />n<sub>β</sub> = 1.559–1.569,<br /> n<sub>γ</sub> = 1.569–1.570
| opticalprop = Biaxial (–)
| pleochroism =
| 2V          = Measured: 24° to 50°, Calculated: 44°
| streak      = White
| gravity     = 2.16–2.68
| melt        =
| fusibility  =
| diagnostic  =
| solubility  =
| references  =<ref name=Mindat>{{Mindat |id=2156 |name=Kaolinite |access-date=5 August 2009}}</ref><ref name=Webmin>{{WebMineral |url=http://www.webmineral.com/data/Kaolinite.shtml |title=Kaolinite Mineral Data |access-date=5 August 2009}}</ref><ref name=Handbook>{{cite book |title=Handbook of Mineralogy: Silica, silicates |publisher=Mineral Data Publishing |year=1995 |isbn=9780962209734 |veditors=Anthony JW, Bideaux RA, Bladh KW, Nichols MC |location=Tucson, Ariz. |chapter=Kaolinite |oclc=928816381 |display-editors=3 |chapter-url=http://www.handbookofmineralogy.org/pdfs/kaolinite.pdf}}</ref>
}}'''Kaolinite''' ({{IPAc-en|ˈ|k|eɪ|.|ə|l|ə|ˌ|n|aɪ|t|,_|-|l|ɪ|-}} {{respell|KAY|ə|lə|nyte|,_|-|lih|-}}; also called '''kaolin''')<ref>{{cite Dictionary.com|kaolinite}}</ref><ref>{{Cite dictionary |url=http://www.lexico.com/definition/kaolinite |archive-url=https://web.archive.org/web/20210125021607/https://www.lexico.com/definition/kaolinite |url-status=dead |archive-date=25 January 2021 |title=kaolinite |dictionary=[[Lexico]] UK English Dictionary |publisher=[[Oxford University Press]]}}</ref><ref>{{cite American Heritage Dictionary|kaolinite}}</ref> is a [[clay mineral]], with the chemical composition [[aluminium|Al]]<sub>2</sub>[[Silicon|Si]]<sub>2</sub>[[Oxygen|O]]<sub>5</sub>([[hydroxide|OH]])<sub>4</sub>. It is a layered [[silicate mineral]], with one [[tetrahedron|tetrahedral]] sheet of silica ({{Chem2|SiO4}}) linked through [[oxygen]] [[atom]]s to one [[octahedron|octahedral]] sheet of [[Aluminium oxide|alumina]] ({{Chem2|AlO6}}).{{sfnp|Deer|Howie|Zussman|1992}}

Kaolinite is a soft, earthy, usually white, mineral (dioctahedral phyllosilicate [[clay]]), produced by the chemical weathering of [[aluminium silicate]] minerals like [[feldspar]]. It has a low [[shrink–swell capacity]] and a low [[cation-exchange capacity]] (1–15 meq/100&nbsp;g).

Rocks that are rich in kaolinite, and [[halloysite]], are known as '''kaolin''' ({{IPAc-en|ˈ|k|eɪ|.|ə|l|ᵻ|n}}) or '''china clay'''.<ref>{{cite book|url=https://books.google.com/books?id=Jq2rpN-6AccC|title=Economic geology: principles and practice: metals, minerals, coal and hydrocarbons – introduction to formation and sustainable exploitation of mineral deposits|last=Pohl|first=Walter L.|publisher=Wiley-Blackwell|year=2011|isbn=9781444336627|location=Chichester, West Sussex|pages=331|name-list-style=vanc}}</ref> In many parts of the world kaolin is colored pink-orange-red by [[iron oxide]], giving it a distinct [[rust]] hue. Lower concentrations of iron oxide yield the white, yellow, or light orange colors of kaolin. Alternating lighter and darker layers are sometimes found, as at [[Providence Canyon State Park]] in Georgia, United States.

Kaolin is an important [[industrial mineral|raw material]] in many industries and applications. Commercial grades of kaolin are supplied and transported as powder, lumps, semi-dried noodle or [[slurry]]. Global production of kaolin in 2021 was estimated to be 45 million tonnes,<ref>'U.S. Geological Survey, Mineral Commodity Summaries, January 2022' USGS, 2022.</ref> with a total market value of US $4.24 billion.<ref>'Kaolin Market Size, Share & Trends Analysis Report By Application, By Region And Segment Forecasts, 2022 - 2030. Grand View Research, 2022</ref>

{{anchor|Etymology|Name}}

==Names==
The [[English language|English]] name ''[[:wikt:kaolin#English|kaolin]]'' was [[linguistic borrowing|borrowed]] in 1727 from [[François Xavier d'Entrecolles]]'s 1712 [[French language|French]] reports on the manufacture of [[Jingdezhen porcelain]].<ref>{{OEtymD|kaolin}}</ref> D'Entrecolles was transcribing the [[Chinese language|Chinese]] term {{lang|zh|{{linktext|高嶺土}}}}, now [[romanization of Chinese|romanized]] as {{translit|zh|gāolǐngtǔ}} in [[pinyin]], taken from the name of the village of Gaoling ("High Ridge") near Ehu in [[Fuliang County]], now part of [[Jiangxi Province]]'s [[Jingdezhen Prefecture]].<ref name="Schroeder-2018">{{cite encyclopedia |last=Schroeder PA |encyclopedia=[[New Georgia Encyclopedia]] |title=Kaolin |url=http://www.georgiaencyclopedia.org/nge/Article.jsp?id=h-1178 |access-date=14 March 2019 |date=31 July 2018 |type=online }}</ref>{{sfnp|Needham & al.|2004|p=[https://books.google.com/books?id=mabcHwmAD5oC&pg=PA220 220]}} The area around the village had become the main source of Jingdezhen's kaolin over the course of the [[Qing dynasty]].{{sfnp|Needham & al.|2004|p=[https://books.google.com/books?id=mabcHwmAD5oC&pg=PA220 220]}} The [[mineralogy|mineralogical]] suffix ''[[:wikt:-ite|-ite]]'' was later added to generalize the name to cover nearly identical minerals from other locations.

Kaolinite is also occasionally discussed under the [[archaism|archaic name]]s '''lithomarge''' and lithomarga from [[Latin]] {{lang|la|lithomarga}}, a combination of {{lang|la|litho-}} ({{langx|grc|{{linktext|λίθος}}}}，{{translit|grc|líthos}}, "stone") and {{lang|la|marga}} ("[[marl]]"). In more proper modern use, lithomarge now refers specifically to a compacted and massive form of kaolin.<ref>{{Cite web|title=Lithomarge|url=https://www.mindat.org/min-32424.html|access-date=2022-02-23|website=www.mindat.org}}</ref>

==Chemistry==
===Notation===
The [[chemical formula]] for kaolinite as written in [[mineralogy]] is {{Chem2|Al2Si2O5(OH)4}},<ref name=Handbook/> however, in [[ceramic engineering|ceramics]] applications the same formula is typically written in terms of oxides, thus giving {{Chem2|Al2O3*2SiO2*2H2O}}.<ref>{{Cite book|title=Handbook of Inorganic Compounds|vauthors=Perry DL|publisher=Taylor & Francis|year=2011|isbn=9781439814611|edition=2nd|location=Boca Raton|oclc=587104373}}</ref>

===Structure===
[[File:Beevers crystal structure model of Kaolinite.jpg|thumb|Kaolinite structure, showing the interlayer hydrogen bonds]]
Compared with other clay minerals, kaolinite is chemically and structurally simple. It is described as a 1:1 or ''TO'' clay mineral because its crystals consist of stacked ''TO'' layers. Each ''TO'' layer consists of a tetrahedral (''T'') sheet composed of silicon and oxygen ions bonded to an octahedral (''O'') sheet composed of oxygen, aluminium, and hydroxyl ions. The ''T'' sheet is so called because each silicon ion is surrounded by four oxygen ions forming a tetrahedron. The ''O'' sheet is so called because each aluminium ion is surrounded by six oxygen or hydroxyl ions arranged at the corners of an octahedron. The two sheets in each layer are strongly bonded together via shared oxygen ions, while layers are bonded via [[hydrogen bonding]] between oxygen on the outer face of the ''T'' sheet of one layer and hydroxyl on the outer face of the ''O'' sheet of the next layer.<ref name="nesse">{{cite book |last1=Nesse |first1=William D. |title=Introduction to mineralogy |date=2000 |publisher=Oxford University Press |location=New York |isbn=9780195106916 |pages=254–255}}</ref>

<gallery>
File:Mica T.png|View of the structure of the tetrahedral (''T'') sheet of kaolinite
File:Mica dO.png|View of the structure of the octahedral (''O'') sheet of kaolinite
File:Kaolinite crystal structure.png|Kaolinite crystal structure looking along the layers
</gallery>

A kaolinite layer has no net electrical charge and so there are no large cations (such as calcium, sodium, or potassium) between layers as with most other clay minerals. This accounts for kaolinite's relatively low ion exchange capacity. The close hydrogen bonding between layers also hinders water molecules from infiltrating between layers, accounting for kaolinite's nonswelling character.<ref name="nesse"/>

When moistened, the tiny platelike crystals of kaolinite acquire a layer of water molecules that cause crystals to adhere to each other and give kaolin clay its cohesiveness. The bonds are weak enough to allow the plates to slip past each other when the clay is being molded, but strong enough to hold the plates in place and allow the molded clay to retain its shape. When the clay is dried, most of the water molecules are removed, and the plates hydrogen bond directly to each other, so that the dried clay is rigid but still fragile. If the clay is moistened again, it will once more become plastic.<ref>{{cite journal |last1=Breuer |first1=Stephen |title=The chemistry of pottery |journal=Education in Chemistry |date=July 2012 |pages=17–20 |url=https://www.qvevriproject.org/Files/2012.07.00_RSC_Breuer_ChemistryOfPottery.pdf |access-date=8 December 2020}}</ref>

===Structural transformations===
Kaolinite group clays undergo a series of phase transformations upon thermal treatment in air at atmospheric pressure.

====Milling====
High-energy milling of kaolin results in the formation of a mechanochemically amorphized phase similar to [[metakaolin]], although the properties of this solid are quite different.<ref name="kaol">{{cite journal|vauthors=Kasa E, Szabados M, Baan K, Konya Z, Kukovecz A, Kutus B, Palinko I, Sipos P|year=2021|title=The dissolution kinetics of raw and mechanochemically treated kaolinites in industrial spent liquor – The effect of the physico-chemical properties of the solids|journal=[[Applied Clay Science|Appl. Clay Sci.]]|volume=203|page=105994|doi=10.1016/j.clay.2021.105994|bibcode=2021ApCS..20305994K |doi-access=free|hdl=21.11116/0000-0008-06AA-2|hdl-access=free}}</ref> The high-energy milling process is highly inefficient and consumes a large amount of energy.<ref>{{cite book |last1=Baláž |first1=Peter |chapter=High-Energy Milling |title=Mechanochemistry in Nanoscience and Minerals Engineering |date=2008 |pages=103–132 |doi=10.1007/978-3-540-74855-7_2|isbn=978-3-540-74854-0 }}</ref>

====Drying====
{{See also|Buell dryer}}
Below 100&nbsp;°C, exposure to low humidity air will result in the slow evaporation of any liquid water in the kaolin. At low moisture content the mass can be described ''leather dry'', and at near 0% moisture it is referred to as ''bone dry''.

Above 100&nbsp;°C any remaining free water is lost. Above around 400&nbsp;°C hydroxyl ions (OH<sup>−</sup>) are lost from the kaolinite crystal structure in the form of water: the material cannot now be plasticised by absorbing water.<ref>'Ceramics Are More Than Clay Alone - Raw Materials, Products, Applications' P. Bormans. Cambridge International Science Publishing, 2004. pg. 180</ref> This is irreversible, as are subsequent transformations; this is referred to as ''calcination''.

====Metakaolin====
Endothermic dehydration of kaolinite begins at 550–600&nbsp;°C producing disordered [[metakaolin]], but continuous [[hydroxyl]] loss is observed up to {{convert|900|C}}.<ref name="b1">{{cite journal|display-authors=3|vauthors=Bellotto M, Gualtieri A, Artioli G, Clark SM|year=1995|title=Kinetic study of the kaolinite-mullite reaction sequence. Part I: kaolinite dehydroxylation|journal=[[Physics and Chemistry of Minerals|Phys. Chem. Miner.]]|volume=22|issue=4|pages=207–214|bibcode=1995PCM....22..207B|doi=10.1007/BF00202253|s2cid=95897543}}</ref> Although historically there was much disagreement concerning the nature of the metakaolin phase, extensive research has led to a general consensus that metakaolin is not a simple mixture of amorphous silica ({{Chem2|SiO2}}) and alumina ({{Chem2|Al2O3}}), but rather a complex amorphous structure that retains some longer-range order (but not [[quasicrystal|strictly crystalline]]) due to stacking of its hexagonal layers.<ref name=b1/>
:<chem>Al2Si2O5(OH)4 -> Al2Si2O7 + 2 H2O</chem>

====Spinel====
Further heating to 925–950&nbsp;°C converts metakaolin to an aluminium-silicon [[spinel]] which is sometimes also referred to as a gamma-alumina type structure:
:<chem>2 Al2Si2O7 -> Si3Al4O12 + SiO2</chem>

====Platelet mullite====
Upon calcination above 1050&nbsp;°C, the spinel phase nucleates and transforms to [[mullite|platelet mullite]] and highly crystalline [[cristobalite]]:
:<chem>3 Si3Al4O12 -> 2 (3 Al2O3 . 2 SiO2) + 5 SiO2</chem>

====Needle mullite====
Finally, at 1400&nbsp;°C the "needle" form of [[mullite]] appears, offering substantial increases in structural strength and heat resistance. This is a structural but not chemical transformation. See [[stoneware]] for more information on this form.

==Occurrence==
[[File:Kaznějov - kaolin quarry.jpg|right|thumb|200px|Kaolin mine in Czech Republic]]
Kaolinite is one of the most common minerals; it is mined, as kaolin, in [[Australia]], [[Brazil]], [[Bulgaria]], [[People's Republic of China|China]], [[Czech Republic]], [[France]], [[Germany]], [[India]], [[Iran]], [[Malaysia]], [[South Africa]], [[South Korea]],  [[Spain]], [[Tanzania]], [[Thailand]], [[United Kingdom]], [[United States]] and [[Vietnam]].<ref name=Mindat/>

Mantles of kaolinite are common in Western and Northern Europe. The ages of these mantles are [[Mesozoic]] to Early Cenozoic.<ref>{{cite journal|author-link=Piotr Migoń|author-link2=Karna Lidmar-Bergström|vauthors=Migoń P, Lidmar-Bergström K|date=2002|title=Deep weathering through time in central and northwestern Europe: problems of dating and interpretation of geological record|journal=Catena|volume=49|issue=1–2|pages=25–40|doi=10.1016/S0341-8162(02)00015-2|bibcode=2002Caten..49...25M }}</ref>

Kaolinite clay occurs in abundance in [[soil]]s that have formed from the chemical [[weathering]] of rocks in hot, moist [[climate]]s; for example in [[tropical rainforest]] areas. Comparing soils along a gradient towards progressively cooler or drier climates, the proportion of kaolinite decreases, while the proportion of other clay minerals such as [[illite]] (in cooler climates) or [[smectite]] (in drier climates) increases. Such climatically related differences in clay mineral content are often used to infer changes in climates in the geological past, where ancient soils have been buried and preserved.<ref>{{Cite journal|date=2000-02-01|title=Unraveling climatic changes from intraprofile variation in oxygen and hydrogen isotopic composition of goethite and kaolinite in laterites: an integrated study from Yaou, French Guiana|url=https://www.sciencedirect.com/science/article/abs/pii/S0016703799002999|journal=Geochimica et Cosmochimica Acta|language=en|volume=64|issue=3|pages=409–426|doi=10.1016/S0016-7037(99)00299-9|issn=0016-7037|last1=Girard|first1=Jean-Pierre|last2=Freyssinet|first2=Philippe|last3=Chazot|first3=Gilles|bibcode=2000GeCoA..64..409G}}</ref>

[[File:China Clay Silos near Par - geograph.org.uk - 30198.jpg|right|thumb|200px|A kaolin processing plant]]
In the ''[[National Institute for Agronomic Study of the Belgian Congo|Institut National pour l'Étude Agronomique au Congo Belge]]'' (INEAC) classification system, soils in which the clay fraction is predominantly kaolinite are called ''kaolisol'' (from kaolin and soil).<ref>{{cite book|title=Tropical soils and soil survey|last=Young|first=Anthony|publisher=CUP Archive|year=1980|isbn=9780521297684|series=Cambridge Geographical Studies|volume=9|pages=132|name-list-style=vanc}}</ref>

In the United States, the main kaolin deposits are found in central [[Georgia (U.S. state)|Georgia]], on a stretch of the [[Atlantic Seaboard fall line]] between [[Augusta, Georgia|Augusta]] and [[Macon, Georgia|Macon]]. This area of thirteen counties is called the "white gold" belt; [[Sandersville, Georgia|Sandersville]] is known as the "Kaolin Capital of the World" due to its abundance of kaolin.<ref name="sandersville-ga">{{cite web|url=http://www.sandersville.net/KaolinCapitaloftheWorld.cfm|title=Kaolin Capital of the World|website=City of Sandersville, GA|access-date=27 August 2018}}</ref><ref name="bitter-southerner">{{cite web|url=http://bittersoutherner.com/eat-white-dirt/|title=Making Peace With the Age-Old Practice of Eating White Dirt|last=Reece C|website=The Bitter Southerner|access-date=27 August 2018}}</ref><ref>{{cite news |last1=Smothers |first1=Ronald |title=White George clay turns into cash |url=https://www.nytimes.com/1987/12/12/us/white-georgia-clay-turns-into-cash.html |access-date=19 January 2021 |work=The New York Times |date=12 December 1987}}</ref> In the late 1800s, an active kaolin surface-mining industry existed in the extreme southeast corner of Pennsylvania, near the towns of [[Landenberg, Pennsylvania|Landenberg]] and [[Kaolin, Pennsylvania|Kaolin]], and in what is present-day White Clay Creek Preserve. The product was brought by train to [[Newark, Delaware]], on the [[Pomeroy and Newark Railroad|Newark-Pomeroy]] line, along which can still be seen many open-pit clay mines. The deposits were formed between the late [[Cretaceous]] and early [[Paleogene]], about 100 to 45 million years ago, in sediments derived from weathered [[Igneous rock|igneous]] and metakaolin rocks.<ref name="Schroeder-2018" /> Kaolin production in the United States during 2011 was 5.5 million tons.<ref>{{cite tech report|last=Virta R|title=Mineral Commodity Summaries|institution=U.S. Geological Survey|pages=44–45|year=2012|url=http://minerals.usgs.gov/minerals/pubs/commodity/clays/mcs-2012-clays.pdf}}</ref>
[[File:Buell Dryer.jpg|right|thumb|200px|A [[Buell dryer]] in the UK, which is used to dry processed kaolin]]
During the [[Paleocene–Eocene Thermal Maximum]] sediments deposited in the [[Espluga Freda]] area of [[Spain]] were enriched with kaolinite from a [[detrital]] source due to [[denudation]].<ref>{{cite journal|display-authors=3|vauthors=Adatte T, Khozyem H, Spangenberg JE, Samant B, Keller G|year=2014|title=Response of terrestrial environment to the Paleocene-Eocene Thermal Maximum (PETM), new insights from India and NE Spain|url=https://www.researchgate.net/publication/263430375|journal=Rendiconti Online della Società Geologica Italiana|volume=31|pages=5–6|doi=10.3301/ROL.2014.17}}</ref>

==Synthesis and genesis==
Difficulties are encountered when trying to explain kaolinite formation under atmospheric conditions by extrapolation of thermodynamic data from the more successful high-temperature syntheses.<ref>{{Cite book|url=https://core.ac.uk/display/29380966|title=Relative stabilities of soil minerals|vauthors=Meijer EL, van der Plas L|publisher=Veenman|year=1980|series=Mededelingen Landbouwhogeschool Wageningen|volume=80|location=Wageningen|pages=18}}</ref> La Iglesia and Van Oosterwijk-Gastuche (1978)<ref>{{Cite journal|vauthors=La Iglesia A, Van Oosterwyck-Gastuche MC|date=1978|title=Kaolinite Synthesis. I. Crystallization Conditions at Low Temperatures and Calculation of Thermodynamic Equilibria. Application to Laboratory and Field Observations|journal=Clays and Clay Minerals|volume=26|issue=6|pages=397–408|doi=10.1346/CCMN.1978.0260603|bibcode=1978CCM....26..397L|doi-access=free}}</ref> thought that the conditions under which kaolinite will nucleate can be deduced from stability diagrams, based as they are on dissolution data. Because of a lack of convincing results in their own experiments, La Iglesia and Van Oosterwijk-Gastuche (1978) had to conclude, however, that there were other, still unknown, factors involved in the low-temperature nucleation of kaolinite. Because of the observed very slow crystallization rates of kaolinite from solution at room temperature Fripiat and Herbillon (1971) postulated the existence of high activation energies in the low-temperature nucleation of kaolinite.

At high temperatures, [[thermodynamic equilibrium|equilibrium]] thermodynamic models appear to be satisfactory for the description of kaolinite dissolution and [[nucleation]], because the thermal energy suffices to overcome the [[energy barrier]]s involved in the [[nucleation]] process. The importance of syntheses at ambient temperature and atmospheric pressure towards the understanding of the mechanism involved in the nucleation of clay minerals lies in overcoming these energy barriers. As indicated by Caillère and Hénin (1960)<ref name="Caillère-1960">{{Cite journal|vauthors=Caillère S, Hénin S|date=1960|title=Vues d'ensemble sur le problème de la synthèse des minéraux argileux à basse température|journal=Bulletin du Groupe français des argiles|language=fr|volume=12|issue=7|pages=63|doi=10.3406/argil.1960.969}}</ref> the processes involved will have to be studied in well-defined experiments, because it is virtually impossible to isolate the factors involved by mere deduction from complex natural physico-chemical systems such as the [[soil]] environment.
Fripiat and Herbillon (1971),<ref>{{Cite book|title=Soils and tropical weathering: proceedings of the Bandung Symposium 16 to 23 November 1969|vauthors=Fripiat JJ, Herbillon AJ|publisher=[[Unesco]]|year=1971|series=Natural resources research|volume=11|location=Paris|pages=15–24|chapter=Formation and transformations of clay minerals in tropical soils|oclc=421565}}</ref> in a review on the formation of kaolinite, raised the fundamental question how a [[Randomness|disordered]] material (i.e., the [[amorphous]] fraction of tropical soils) could ever be transformed into a corresponding ordered structure. This transformation seems to take place in soils without major changes in the environment, in a relatively short period of time, and at ambient [[temperature]] (and [[pressure]]).

Low-temperature synthesis of clay minerals (with kaolinite as an example) has several aspects. In the first place the silicic acid to be supplied to the growing crystal must be in a monomeric form, i.e., silica should be present in very dilute solution (Caillère et al., 1957;<ref>{{Cite journal|vauthors=Caillère S, Hénin S, Esquevin J|date=1957|title=Synthèse des minéraux argileux.|journal=Bulletin du Groupe français des argiles|language=fr|volume=9|issue=4|pages=67–76|doi=10.3406/argil.1957.940}}</ref> Caillère and Hénin, 1960;<ref name="Caillère-1960" /> Wey and Siffert, 1962;<ref>{{Cite journal|vauthors=Wey R, Siffert B|date=1961|title=Réactions de la silice monomoléculaire en solutions avec les ions Al3+ et Mg2+|journal=Colloques Internationaux|language=fr|publisher=Centre National des Recherches Scientifiques|volume=105|pages=11–23}}</ref> Millot, 1970<ref>{{Cite book|title=Geology of Clays|last=Millot|first=Georges|publisher=Springer-Verlag|year=1970|isbn=9783662416099|location=New York|translator-last=Paquet|translator-first=H.|doi=10.1007/978-3-662-41609-9|s2cid=128831318 |name-list-style=vanc|translator-last2=Farrand|translator-first2=W. R.}}</ref>). In order to prevent the formation of [[amorphous]] [[silica]] [[gel]]s precipitating from supersaturated solutions without reacting with the [[aluminium]] or [[magnesium]] [[cation]]s to form crystalline [[silicate]]s, the [[silicic acid]] must be present in concentrations below the maximum solubility of amorphous silica. The principle behind this prerequisite can be found in structural chemistry: "Since the polysilicate ions are not of uniform size, they cannot arrange themselves along with the metal ions into a regular crystal lattice." (Iler, 1955, p.&nbsp;182<ref>{{Cite book|title=The colloid chemistry of silica and silicates|last=Iler|first=R. K.|publisher=Cornell University Press|year=1955|location=Ithaca, N.Y.|name-list-style=vanc}}</ref>)

The second aspect of the low-temperature synthesis of kaolinite is that the [[aluminium]] cations must be hexacoordinated with respect to [[oxygen]] (Caillère and Hénin, 1947;<ref>{{Cite journal|vauthors=Caillère S, Hénin S|date=1947|title=Formation d'une phyllite du type kaolinique par traitement d'une montmorillonite|journal=Comptes Rendus de l'Académie des Sciences de Paris|volume=224|issue=1|pages=53–55}}</ref> Caillère et al., 1953;<ref>{{Cite journal|vauthors=Caillère S, Hénin S, Esquevin J|date=1953|title=Recherches sur la synthèse des minéraux argileux|journal=Bulletin de la Société française de Minéralogie et de Cristallographie|language=fr|volume=76|issue=7|pages=300–314|doi=10.3406/bulmi.1953.4841}}</ref> Hénin and Robichet, 1955<ref>{{Cite journal|vauthors=Hénin S, Robichet O|date=1955|title=Résultats obtenus au cours de nouveaux essais de synthèse de minéraux argileux|journal=Bulletin du Groupe français des argiles|language=fr|volume=6|issue=1|pages=19–22|doi=10.3406/argil.1955.1257}}</ref>). Gastuche et al. (1962)<ref>{{Cite journal|vauthors=Gastuche MC, Fripiat JJ, DeKimpe C|date=1962|title=La genèse des minéraux argileux de la famille du kaolin. I. – Aspect colloidal|journal=Colloque C.N.R.S.|volume=105|pages=57–65}}</ref> and Caillère and Hénin (1962) have concluded that kaolinite can only ever be formed when the aluminium hydroxide is in the form of [[gibbsite]]. Otherwise, the precipitate formed will be a "mixed alumino-silicic gel" (as Millot, 1970, p.&nbsp;343 put it). If it were the only requirement, large amounts of kaolinite could be harvested simply by adding gibbsite powder to a silica solution. Undoubtedly a marked degree of adsorption of the silica in solution by the gibbsite surfaces will take place, but, as stated before, mere adsorption does not create the layer lattice typical of kaolinite crystals.

The third aspect is that these two initial components must be incorporated into one mixed crystal with a layer structure. From the following equation (as given by Gastuche and DeKimpe, 1962)<ref>{{Cite journal|vauthors=Gastuche MC, DeKimpe C|date=1962|title=La genèse des minéraux argileux de la famille du kaolin. II. Aspect cristallin|journal=Colloque C.N.R.S.|volume=105|pages=75–88}}</ref> for kaolinite formation
:<chem>2Al(OH)3 + 2H4SiO4 -> Si2O5 . Al2(OH)4 + 5H2O</chem>
it can be seen that five molecules of water must be removed from the reaction for every [[molecule]] of kaolinite formed. Field evidence illustrating the importance of the removal of water from the kaolinite reaction has been supplied by Gastuche and DeKimpe (1962). While studying [[soil formation]] on a [[basalt]]ic rock in [[Kivu]] ([[Zaïre]]), they noted how the occurrence of kaolinite depended on the {{lang|fr|"degrée de drainage"}} of the area involved. A clear distinction was found between areas with good [[drainage]] (i.e., areas with a marked difference between wet and dry seasons) and those areas with poor [[drainage]] (i.e., [[perennial]]ly [[swamp]]y areas). Kaolinite was only found in the areas with distinct seasonal alternations between wet and dry. The possible significance of alternating wet and dry conditions on the transition of [[allophane]] into kaolinite has been stressed by Tamura and Jackson (1953).<ref>{{Cite journal|last=Tamura T, Jackson ML|date=1953|title=Structural and Energy Relationships in the Formation of Iron and Aluminum Oxides, Hydroxides, and Silicates|journal=[[Science (journal)|Science]]|volume=117|issue=3041|pages=381–383|doi=10.1126/science.117.3041.381|pmid=17749950|bibcode=1953Sci...117..381T}}</ref> The role of alternations between wetting and drying on the formation of kaolinite has also been noted by Moore (1964).<ref>{{Cite journal|vauthors=Moore LR|date=1964|title=The in Situ Formation and Development of Some Kaolinite Macrocrystals|url=https://www.cambridge.org/core/journals/clay-minerals-bulletin/article/in-situ-formation-and-development-of-some-kaolinite-macrocrystals/3B15F40C24CBDF3AF6128FC3C0963C2D|journal=[[Clay Minerals]]|volume=5|issue=31|pages=338–352|doi=10.1180/claymin.1964.005.31.02|bibcode=1964ClMin...5..338M}}</ref>

===Laboratory syntheses===
Syntheses of kaolinite at high temperatures (more than {{convert|100|C|disp=sqbr}}) are relatively well known. There are for example the syntheses of Van Nieuwenberg and Pieters (1929);<ref>{{Cite journal|vauthors=van Nieuwenburg CJ, Pieters HA|date=1929|title=Studies on hydrated aluminium silicates: I. The rehydration of metakaolin and the synthesis of kaolin|journal=[[Recueil des Travaux Chimiques des Pays-Bas|Recl. Trav. Chim. Pays-Bas]]|volume=48|issue=1|pages=27–36|doi=10.1002/recl.19290480106}}</ref> Noll (1934);<ref>{{Cite journal|vauthors=Noll W|date=1934|title=Hydrothermale Synthese des Kaolins|journal=Zeitschrift für Kristallographie, Mineralogie und Petrographie|language=de|volume=45|issue=2–3|pages=175–190|doi=10.1007/BF02943371|bibcode=1934ZKMP...45..175N|s2cid=96869398}}</ref> Noll (1936);<ref>{{Cite journal|vauthors=Noll W|date=1936|title=Über die Bildungsbedingungen von Kaolin, Montmorillonit, Sericit, Pyrophyllit und Analcim|journal=Zeitschrift für Kristallographie, Mineralogie und Petrographie|language=de|volume=48|issue=3–4|pages=210–247|doi=10.1007/BF02939458|bibcode=1936ZKMP...48..210N|s2cid=128744123}}</ref> Norton (1939);<ref>{{Cite journal|vauthors=Norton FH|date=1939|title=Hydrothermal formation of clay minerals in the laboratory|url=https://pubs.geoscienceworld.org/msa/ammin/article-abstract/24/1/1/537069/hydrothermal-formation-of-clay-minerals-in-the|journal=[[American Mineralogist|Am. Mineral.]]|volume=24|issue=1|pages=1–17}}</ref> Roy and Osborn (1954);<ref>{{Cite journal|vauthors=Roy R, Osborn EF|date=1954|title=The system Al<sub>2</sub>O<sub>3</sub>-SiO<sub>2</sub>-H<sub>2</sub>O |url=https://pubs.geoscienceworld.org/msa/ammin/article-abstract/39/11-12/853/539421/the-system-al2o3-sio2-h2o|journal=[[American Mineralogist|Am. Mineral.]]|volume=39|issue=11–12|pages=853–885}}</ref> Roy (1961);<ref>{{Cite journal|vauthors=Roy R|date=1962|title=The preparation and properties of synthetic clay minerals|journal=Colloque C.N.R.S.|volume=105|pages=83–98}}</ref> Hawkins and Roy (1962);<ref>{{Cite journal|vauthors=Hawkins DB, Roy R|date=1962|title=Electrolytic Synthesis of Kaolinite Under Hydrothermal Conditions|journal=[[Journal of the American Ceramic Society|J. Am. Ceram. Soc.]]|volume=45|issue=10|pages=507–508|doi=10.1111/j.1151-2916.1962.tb11044.x}}</ref> Tomura et al. (1985);<ref>{{Cite journal|display-authors=3|vauthors=Tomura S, Shibasaki Y, Mizuta H, Kitamura M|date=1985|title=Growth Conditions and Genesis of Spherical and Platy Kaolinite|journal=Clays and Clay Minerals|volume=33|issue=3|pages=200–206|doi=10.1346/CCMN.1985.0330305|bibcode=1985CCM....33..200T|doi-access=free}}</ref> Satokawa et al. (1994)<ref>{{Cite journal|display-authors=3|vauthors=Satokawa S, Osaki Y, Samejima S, Miyawaki R, Tomura S, Shibasaki Y, Sugahara Y|date=1994|title=Effects of the Structure of Silica-Alumina Gel on the Hydrothermal Synthesis of Kaolinite|journal=Clays and Clay Minerals|volume=42|issue=3|pages=288–297|doi=10.1346/CCMN.1994.0420307|bibcode=1994CCM....42..288S|doi-access=free}}</ref> and Huertas et al. (1999).<ref>{{Cite journal|display-authors=3|vauthors=Huertas FJ, Fiore S, Huertas F, Linares J|date=1999|title=Experimental study of the hydrothermal formation of kaolinite|journal=Chemical Geology|volume=156|issue=1–4|pages=171–190|doi=10.1016/S0009-2541(98)00180-6|bibcode=1999ChGeo.156..171H}}</ref>
Relatively few low-temperature syntheses have become known (cf. Brindley and DeKimpe (1961);<ref>{{Cite journal|vauthors=Brindley GW, De Kimpe C|date=1961|title=Attempted Low-Temperature Syntheses of Kaolin Minerals|journal=[[Nature (journal)|Nature]]|volume=190|issue=4772|pages=254|doi=10.1038/190254a0|bibcode=1961Natur.190..254B|s2cid=4149442|doi-access=free}}</ref> DeKimpe (1969);<ref>{{Cite journal|vauthors=De Kimpe CR|date=1969|title=Crystallization of kaolinite at low temperature from an alumino-silicic gel|journal=Clays and Clay Minerals|volume=17|issue=1|pages=37–38|doi=10.1346/CCMN.1969.0170107|bibcode=1969CCM....17...37D|doi-access=free}}</ref> Bogatyrev et al. (1997)<ref>{{Cite journal|display-authors=3|vauthors=Bogatyrev BA, Mateeva LA, Zhukov VV, Magazina LO|date=1997|title=Low-temperature synthesis of kaolinite and halloysite on the gibbsite – silicic acid solution system|journal=Transactions (Doklady) of the Russian Academy of Sciences|series=Earth science sections|volume=353 A|pages=403–405}}</ref>).

Laboratory syntheses of kaolinite at room temperature and atmospheric pressure have been described by DeKimpe et al. (1961).<ref>{{Cite journal|vauthors=DeKimpe CR, Gastuche MC, Brindley GW|date=1961|title=Ionic coordination in alumino-silicic acids in relation to clay mineral formation|url=http://rruff.info/doclib/am/vol46/AM46_1370.pdf|journal=[[American Mineralogist|Am. Mineral.]]|volume=46|issue=11–12|pages=1370–1381}}</ref> From those tests the role of periodicity becomes convincingly clear. DeKimpe et al. (1961) had used daily additions of [[alumina]] (as {{Chem2|AlCl3*6 H2O}}) and [[silica]] (in the form of [[ethyl silicate]]) during at least two months. In addition, adjustments of the pH took place every day by way of adding either [[hydrochloric acid]] or [[sodium hydroxide]]. Such daily additions of Si and Al to the solution in combination with the daily titrations with [[hydrochloric acid]] or [[sodium hydroxide]] during at least 60 days will have introduced the necessary element of periodicity. Only now the actual role of what has been described as the "aging" (''Alterung'') of amorphous alumino-silicates (as for example Harder, 1978<ref>{{Cite journal|vauthors=Harder H|date=1978|title=Synthesen von Tonmineralen unter spezieller Berücksichtigung festländischer Bedingungen|journal=Schriftenreihe für geologische Wissenschaften (Berlin)|language=de|volume=11|pages=51–78}}</ref> had noted) can be fully understood. As such, time is not bringing about any change in a closed system at equilibrium; but a series of alternations of periodically changing conditions (by definition, taking place in an open system) will bring about the low-temperature formation of more and more of the stable phase kaolinite instead of (ill-defined) amorphous alumino-silicates.

==Applications==
===Main===
In 2009, up to 70% of kaolin was used in the production of [[paper]]. Following reduced demand from the paper industry, resulting from both competing minerals and the effect of digital media, in 2016 the market share was reported to be: paper, 36%; ceramics, 31%; paint, 7% and other, 26%.<ref name="Ceramics' F. Hart 2019. Pg.28">'Positive Outlook For Kaolin In Ceramics' F. Hart, I. Wilson. Industrial Minerals, April 2019. Pg.28</ref><ref>{{cite journal |last1=King |first1=R.J. |title=Kaolinite |journal=Geology Today |date=March 2009 |volume=25 |issue=2 |pages=75–78 |doi=10.1111/j.1365-2451.2009.00711.x|bibcode=2009GeolT..25...75K |s2cid=242917623 }}</ref> According to the [[United States Geological Survey|USGS]], in 2021 the global production of kaolin was estimated to be around 45 million tonnes.<ref>U.S. Geological Survey, Mineral Commodity Summaries, January 2022</ref>

* '''Paper''' applications require high-brightness, low abrasion and delaminated kaolins. For paper coatings it is used to enhance the gloss, brilliance, smoothness and receptability to inks; it can account for 25% of mass of the paper. As a paper filler it is used as a pulp extender, and to increase opacity; it can account for 15% of mass.<ref>’Industrial Minerals And Their Uses - A Handbook And Formulary. P. A. Ciullo. William Andrew, 1996. Pg. 43</ref><ref name="Markets And Industry Outlook 2013. Pg. 332">'Kaolin - Global Markets And Industry Outlook' 13th edition. Roskill Information Services, 2013. Pg. 332</ref><ref>{{Cite journal|vauthors=Murray HH, Lyons SC|date=1955|title=Correlation of Paper-Coating Quality with Degree of Crystal Perfection of Kaolinite|journal=Clays and Clay Minerals|volume=4|issue=1|pages=31–40|doi=10.1346/CCMN.1955.0040105|bibcode=1955CCM.....4...31M|doi-access=free}}</ref>
* In whiteware '''ceramic''' bodies, kaolin can constitute up to 50% of the raw materials. In unfired bodies it contributes to the green strength, plasticity and rheological properties, such as the casting rate. During firing it reacts with other body components to form the crystal and glass phases. With suitable firing schedules it is key to the formation of [[mullite]]. The most valued grades have low contents of chromophoric oxides such that the fired material has high whiteness.<ref>’Industrial Minerals And Their Uses - A Handbook And Formular’ P. A. Ciullo. William Andrew, 1996. Pg. 43</ref><ref name="Markets And Industry Outlook 2013. Pg. 332"/><ref>’Dictionary Of Ceramic Science And Engineering' L. S. O’Bannon. Plenum Press / Springer. 1984. Pg.146</ref><ref>’Dictionary Of Ceramic Science And Engineering’ 3rd edition. I. MCcolm. Springer, 2013</ref> In glazes it is primarily used as a rheology control agent, but also contributes some green strength. In both glazes and frits it contributes some SiO<sub>2</sub> as a glass network former, and Al<sub>2</sub>O<sub>3</sub> as both a network former and modifier.<ref>'Ceramics Glaze Technology.' J.R.Taylor & A.C.Bull. The Institute Of Ceramics/Pergamon Press986</ref>

===Other industrial===
* As a raw material for the production of an insulation material called Kaowool (a form of [[Mineral wool#Kaowool|mineral wool]]).
* An additive to some [[paint]]s to extend the [[titanium dioxide]] ({{Chem2|TiO2}}) white pigment and modify gloss levels.
* An additive to modify the properties of [[rubber]] upon [[vulcanization]].
* An additive to adhesives to modify [[rheology]].<ref>{{cite book|url=https://books.google.com/books?id=qQPozu9fWrIC&pg=PA43|title=Industrial Minerals and Their Uses: A Handbook and Formulary|last=Ciullo|first=Peter A.|publisher=Noyes Publications|year=1996|isbn=9780815518082|location=Westwood, NJ|pages=41–43|name-list-style=vanc}}</ref>
* As adsorbents in water and wastewater treatment.<ref>{{cite journal|display-authors=3|vauthors=Leiviskä T, Gehör S, Eijärvi E, Sarpola A, Tanskanen J|date=2012|title=Characteristics and potential applications of coarse clay fractions from Puolanka, Finland|journal=[[Open Engineering|Open Eng.]]|volume=2|issue=2|pages=239–247|bibcode=2012CEJE....2..239L|doi=10.2478/s13531-011-0067-9|doi-access=free}}</ref>
* In its altered [[metakaolin]] form, as a [[pozzolan]]; when added to a concrete mix, metakaolin accelerates the hydration of [[Portland cement]] and takes part in the [[pozzolanic reaction]] with the [[portlandite]] formed in the hydration of the main cement minerals (e.g. [[alite]]).
* [[Metakaolin]] is also a base component for [[geopolymer]] compounds.

===Medical===
* To soothe an upset [[stomach]], similar to the way [[parrot]]s (and later, humans) in [[South America]] originally used it<ref>{{Cite journal|vauthors=Diamond JM|date=1999|title=Dirty eating for healthy living|journal=[[Nature (journal)|Nature]]|series=Evolutionary biology|volume=400|issue=6740|pages=120–121|bibcode=1999Natur.400..120D|doi=10.1038/22014|pmid=10408435|doi-access=free}}</ref> (more recently, industrially produced).
* Kaolin-based preparations are used for treatment of [[diarrhea]].
* An ingredient in 'pre-work' skin protection and [[barrier cream]]s.<ref>{{cite web|url=https://www.debgroup.com/sites/default/files/uploads/product-sheets/en-us/stokoderm_protect_pure_pi.pdf|title=Stokoderm Protect PURE|date=2017|website=debgroup.com|publisher=Deb USA, Inc.|type=product leaflet|access-date=12 April 2018}}</ref>
* To induce and accelerate blood clotting. In April 2008 the US [[Naval Medical Research Institute]] announced the successful use of a kaolinite-derived [[aluminosilicate]] infusion in traditional [[gauze]].<ref>{{cite news|url=https://www.wired.com/medtech/health/news/2008/04/blood_clotting|title=Nanoparticles Help Gauze Stop Gushing Wounds|last=Rowe A|date=24 April 2008|magazine=Wired|access-date=5 August 2009|archive-url=https://web.archive.org/web/20090706091649/http://www.wired.com/medtech/health/news/2008/04/blood_clotting|archive-date=6 July 2009|url-status=live|publisher=Condé Nast}}</ref> which is still the hemostat of choice for all branches of the US military. See [[Kaolin clotting time]] and [[QuikClot]].
* As a mild abrasive in [[toothpaste]].

===Cosmetics===
* As a filler in [[cosmetics]].
* For facial masks or soap.
* for spa body treatments, such as body wraps, cocoons, or spot treatments.

===Archaeology===
* As an indicator in [[radiological dating]] since kaolinite can contain very small traces of [[uranium]] and [[thorium]].

===Geophagy===
* Humans sometimes eat kaolin for pleasure or to suppress hunger,<ref name="Balengou">{{Cite news|url=http://www.quotidienlejour.com/double-page-/reportage/504-balengou-autour-des-mines|title=Balengou: autour des mines|last=Kamtche F|date=2012|work=Le Jour|access-date=22 March 2019|archive-url=https://web.archive.org/web/20120304025224/http://www.quotidienlejour.com/double-page-/reportage/504-balengou-autour-des-mines|archive-date=4 March 2012|url-status=dead|language=fr|trans-title=Balengou: around the mines}}</ref> a practice known as [[geophagy]].  In Africa, kaolin used for such purposes is known as ''kalaba'' (in [[Gabon]]<ref>Karine Boucher, Suzanne Lafage. [http://www.unice.fr/ILF-CNRS/ofcaf/14/K14.html "Le lexique français du Gabon: K."] ''Le Français en Afrique: Revue du Réseau des Observatoires du Français Contemporain en Afrique''. 2000.</ref> and [[Cameroon]]<ref name="Balengou"/>), ''calaba'', and ''calabachop'' (in [[Equatorial Guinea]]).  Consumption is greater among women, especially during pregnancy,<ref>Gerald N. Callahan. [http://www.cdc.gov/ncidod/EID/vol9no8/03-0033.htm "Eating Dirt."] ''[[Emerging Infectious Diseases]]''. 9.8 (August 2003).</ref> and its use is sometimes said by women of the region to be a habit analogous to cigarette smoking among men. The practice has also been observed within a small population of African-American women in the [[Southern United States]], especially [[Georgia (U.S. state)|Georgia]], likely brought with the traditions of the aforementioned Africans via [[Slavery in the United States|slavery]].<ref name="Clay Eating">{{Cite encyclopedia|title=Clay Eating|date=3 February 2004|encyclopedia=[[New Georgia Encyclopedia]]|last=Grigsby RK|series=Science & Medicine|type=online|url=https://www.georgiaencyclopedia.org/articles/science-medicine/clay-eating|access-date=2019-10-20}}</ref><ref>{{Cite news|url=https://www.npr.org/sections/thesalt/2014/04/02/297881388/the-old-and-mysterious-practice-of-eating-dirt-revealed?t=1553254886529|title=The Old And Mysterious Practice of Eating Dirt, Revealed|last=Chen L|date=2 April 2014|work=The Salt|publisher=NPR}}</ref> There, the kaolin is called ''white dirt'', ''chalk'' or ''white clay''.<ref name="Clay Eating"/>

===Geotechnical engineering===
* Research results show that the utilization of kaolinite in [[geotechnical engineering]] can be alternatively replaced by safer illite, especially if its presence is less than 10.8% of the total rock mass.<ref>{{cite journal |last1=Supandi |first1=Supandi |last2=Zakaria |first2=Zufialdi |last3=Sukiyah |first3=Emi |last4=Sudradjat |first4=Adjat |title=The Influence of Kaolinite - Illite toward mechanical properties of Claystone |journal=Open Geosciences |date=2019-08-29 |volume=11 |issue=1 |pages=440–446 |doi=10.1515/geo-2019-0035|bibcode=2019OGeo...11...35S |doi-access=free }}</ref>

===Small-scale uses===
* As a light-diffusing material in white [[incandescent light bulb]]s.
* In [[organic farming]] as a [[kaolin spray|spray]] applied to crops to deter [[Codling moth|insect]] damage, and in the case of apples, to prevent sun scald.
* As [[whitewash]] in traditional stone masonry homes in Nepal.
* As a filler in [[Edison Disc Record|Edison Diamond Discs]].<ref>{{Cite web|url=http://www.gracyk.com/diamonddisc.shtml|title=Edison Diamond Discs: 1912 - 1929|last=Gracyk T|date=2006|website=Tim Gracyk's Phonographs, Singers, & Old Records|access-date=22 March 2019}}</ref>

==Production output==
Global production of kaolin by country in 2012 was estimated to be:<ref>'Kaolin - Global Markets And Industry Outlook' 13th edition. Roskill Information Services, 2013. Pgs. 28-30</ref>
{| class="wikitable sortable collapsible"
|+'000 tonnes
! Global - total !! 26,651
|-
! 
| 
|-
! Egypt
| 275
|-
! Nigeria
| 100
|-
! Algeria
| 80
|-
! Tanzania
| 45
|-
! Sudan
| 35
|-
! Uganda
| 30
|-
! South Africa
| 15
|-
! Ethiopia
| 2
|-
! Kenya
| 1
|-
! Africa - total
| 583
|-
! 
| 
|-
! China
| 3,950
|-
! South Korea
| 800
|-
! Vietnam
| 650
|-
! Malaysia
| 450
|-
! Thailand
| 180
|-
! Indonesia'
| 175
|-
! India
| 75
|-
! Bangladesh
| 20
|-
! Taiwan
| 17
|-
! Pakistan
| 15
|-
! Sri Lanka
| 11
|-
! Japan
| 3
|-
! Philippines
| 2
|-
! Asia - total
| 6,348
|-
! 
| 
|-
! Germany
| 4,800
|-
! UK
| 1,000
|-
! Czech Republic
| 650
|-
! Italy
| 625
|-
! France
| 350
|-
! Portugal
| 325
|-
! Spain
| 300
|-
! [[Bosnia and Herzegovina|Bosnia–Herzegovina]]
| 250
|-
! Bulgaria
| 225
|-
! Russia
| 170
|-
! Poland
| 125
|-
! Ukraine
| 100
|-
! Serbia
| 90
|-
! Austria
| 65
|-
! Denmark
| 3
|-
! Europe - total
| 9,078
|-
! 
| 
|-
! USA
| 5,900
|-
! Mexico
| 120
|-
! N. America - total
| 6,020
|-
! 
| 
|-
! Iran
| 1,500
|-
! Turkey
| 725
|-
! Jordan
| 100
|-
! Saudi Arabia
| 70
|-
! Iraq
| 3
|-
! Middle East - total
| 2,398
|-
! 
| 
|-
! Australia
| 40
|-
! New Zealand
| 11
|-
! Oceania - total
| 51
|-
! 
| 
|-
! Brazil
| 1,900
|-
! Argentina
| 80
|-
! Paraguay
| 66
|-
! Chile
| 60
|-
! Colombia
| 20
|-
! Peru
| 20
|-
! Ecuador
| 15
|-
! Venezuela
| 10
|-
! Guatemala
| 2
|-
! S. & C. America - total
| 2,173
|}

==Typical properties==
Some selected typical properties of various ceramic grade kaolins are:<ref name="Ceramics' F. Hart 2019. Pg.28"/>

{| class="wikitable collapsible"
! Product name !! SSP !! Premium !! Longyan 325# !! Zettlitz 1A !! OKA
|-
! Country
| UK || New Zealand || China || Czech Republic || Germany
|-
! Manufacturer
| Imerys || Imerys || Logyan || Sedlecky || AKW
|-
! 
|  ||  ||  ||  || 
|-
! % < 2 μm
| 85 || 97 || 25 || 56 || 82
|-
! % <1 μm
| 50 || 88 || 15 || 41 || 50
|-
! 
|  ||  ||  ||  || 
|-
! SiO<sub>2</sub>, %
| 48.0 || 49.5 || 49.3 || 48.0 || 49.5
|-
! Al<sub>2</sub>O<sub>3</sub>, %
| 37.0 || 35.5 || 35.5 || 37.0 || 35.5
|-
! Fe<sub>2</sub>O<sub>3</sub>, %
| 0.44 || 0.29 || 0.22 || 0.68 || 0.43
|-
! TiO<sub>2</sub>, %
| 0.01 || 0.09 || 0.01 || 0.20 || 0.17
|-
! CaO, %
| 0.10 ||  -|| 0.03 || 0.08 || 0.20
|-
! MgO, %
| 0.25 ||  -|| 0.25 || 0.23 || 0.02
|-
! K<sub>2</sub>O, %
| 1.25 || -|| 1.90 || 0.92 || 0.30
|-
! Na<sub>2</sub>O, %
| 0.15 ||  -|| 0.09 || 0.07 || 0.01
|-
! [[Loss on ignition|LOI]]%
| 12.8 || 13.8 || 11.9 || 12.9 || 13.4
|-
! 
|  ||  ||  ||  || 
|-
! Kaolinite, %
| 95 ||  -|| 40 || 89 || 86
|-
! Halloysite, %
|  -|| 92 || 40 ||  -|| -
|-
! Mica, %
| 4 ||  -||  -||  -|| -
|-
! Quartz, %
| 1 || 4 || 3 || 1 || 8
|-
! Smectite, %
|  -||  -||  -|| 1 || 6
|-
! Cristobalite, %
|  -|| 4 ||  -||  -|| -
|}

==Safety==
{{NFPA 704 | H= 1 | F= 0 | R= 0 | S= |caption=Kaolin |ref=<ref name=MSDS>{{cite web |title=Material Safety Data Sheet: Kaolin |url=https://www.conncoll.edu/media/website-media/offices/ehs/envhealthdocs/Tile-6_Kaolin.pdf |website=Connecticut College |publisher=Imerys Pigments and Additives Group |access-date=11 November 2021}}</ref>}}
Kaolin is [[generally recognized as safe]], but may cause mild irritation of the skin or mucous membranes. Kaolin products may also contain traces of [[crystalline silica]], a known [[carcinogen]] if inhaled.<ref name=MSDS/>

In the US, the [[Occupational Safety and Health Administration]] (OSHA) has set the legal limit ([[permissible exposure limit]]) for kaolin exposure in the workplace as 15&nbsp;mg/m<sup>3</sup> total exposure and 5&nbsp;mg/m<sup>3</sup> respiratory exposure over an 8-hour workday. The [[National Institute for Occupational Safety and Health]] (NIOSH) has set a [[recommended exposure limit]] (REL) of 10&nbsp;mg/m<sup>3</sup> total exposure TWA 5&nbsp;mg/m<sup>3</sup> respiratory exposure over an 8-hour workday.<ref>{{Cite web|url=https://www.cdc.gov/niosh/npg/npgd0364.html|title=Kaolin|website=[[National Institute for Occupational Safety and Health|NIOSH]] Pocket Guide to Chemical Hazards|publisher=[[Centers for Disease Control and Prevention|CDC]]|access-date=6 November 2015}}</ref>

==See also==
{{colbegin}}
* {{annotated link|China stone}}
* {{annotated link|Clay pit}}
* {{annotated link|Dickite}}
* {{annotated link|Halloysite}}
* {{annotated link|Kaolin Deposits of Charentes Basin, France}}
* {{annotated link|Kaolin spray}}
* {{annotated link|Medicinal clay}}
* {{annotated link|Nacrite}}
* {{annotated link|Cornish China Clay Branches}}
{{colend}}

==References==

===Citations===
{{Reflist}}

===General references===
{{refbegin}}
* {{Cite book |title=Zeolite Molecular Sieves |last=Breck |first=D. W. |publisher=R.E. Krieger Publishing Co. |year=1984 |isbn=0898746485 |location=[[Malabar, Florida|Malabar]] |pages=314–315 }}
* {{Cite book |title=An Introduction to the Rock-Forming Minerals |last1=Deer |first1=W. A. |last2=Howie|first2=R.A. |last3=Zussman|first3=J. |publisher=Longman |year=1992 |isbn=0582300940 |edition=2nd |location=Harlow |title-link=An Introduction to the Rock-Forming Minerals }}
* {{Cite book|title=Manual of Mineralogy... |author3=J.D. Dana |last=Hurlbut |first=C. S. |author2=C. Klein |display-authors=1 |ref={{harvid|Hurlbut & al.|1985}} |publisher=Wiley |year=1985 |isbn=0471805807 |edition=20th |pages=[https://archive.org/details/manualofmineralo00klei/page/428 428–429] |url-access=registration |url=https://archive.org/details/manualofmineralo00klei/page/428 }}
* {{citation |last=Needham |first=Joseph |author2=Rose Kerr |author3=Nigel Wood |author4=Ts'ai Mei-fen |author5=Zhang Fukang |display-authors=1 |ref={{harvid|Needham & al.|2004}} |date=2004 |author-link=Joseph Needham |url=https://books.google.com/books?id=mabcHwmAD5oC |title=Science and Civilisation in China, ''Vol. 5:'' Chemistry and Chemical Technology, ''Part XII:'' Ceramic Technology |editor=Rose Kerr |editor2=Christopher Cullen |display-editors=0 |location=[[Cambridge, England|Cambridge]] |publisher=Cambridge University Press |isbn=0-521-83833-9 |contribution=Chinese Porcelain and the City of Ching-te-chen |contribution-url=https://books.google.com/books?id=mabcHwmAD5oC&pg=PA184 |pages=[https://books.google.com/books?id=mabcHwmAD5oC&pg=PA184 184–240] }}.
* {{cite journal |url=http://www.elementsmagazine.org/toc/toc_v10n3.pdf |access-date=14 September 2022 |title=Kaolin |date = June 2014 | volume=10 | number=3 |editor-last1=Schroeder |editor-first1=Paul A. |editor-last2=Erickson |editor-first2=Gary |display-editors=1 |ref={{harvid|Schroeder & al.|2022}} |journal=Elements}}
{{refend}}

==External links==
* [https://www.cdc.gov/niosh/npg/npgd0364.html CDC – NIOSH Pocket Guide to Chemical Hazards]

{{Phyllosilicates}}
{{Clay minerals}}
{{Authority control}}

[[Category:Aluminium minerals]]
[[Category:Aluminosilicates]]
[[Category:Clay minerals group]]
[[Category:Industrial minerals]]
[[Category:Medicinal clay]]
[[Category:Phyllosilicates]]
[[Category:Triclinic minerals]]
[[Category:Minerals in space group 1]]