Editing Kaolinite (section)

===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.