Editing Kaolinite (section)

===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>