Phyllosilicate

Phyllosilicates are silicate minerals whose structures contain sheets of linked silicon–oxygen tetrahedra, commonly joined to sheets of metal-centered octahedra.

Silicate mineral: A mineral built from silicon–oxygen polyhedra linked in a crystalline structure. Phyllosilicates are one structural class within the silicate minerals.
Tetrahedral-octahedral-tetrahedral layer: A phyllosilicate layer formed by an octahedral sheet sandwiched between two tetrahedral sheets. This three-sheet architecture defines many common clay minerals and micas.
Soil clay: The fine-grained mineral fraction of soil, often dominated by clay minerals. Phyllosilicates supply much of clay soil's surface area and ion-retention capacity.
Nesosilicate: A silicate mineral class whose isolated silicon–oxygen tetrahedra are not linked directly to one another. Unlike phyllosilicates, nesosilicates do not build continuous tetrahedral sheets.
Silicon–oxygen tetrahedron: A structural unit with one silicon atom surrounded by four oxygen atoms. Sharing oxygen atoms between tetrahedra produces the sheets characteristic of this mineral class.
Basal cleavage: Breakage of a mineral along planes parallel to its structural layers. Weak bonding between phyllosilicate layers produces their characteristic sheet-like splitting.
Bentonite: A clay-rich rock composed largely of swelling smectite minerals, especially montmorillonite. Its swelling and sealing behavior make this phyllosilicate-rich material useful in drilling and containment.
Inosilicate: A silicate mineral class built from silicon–oxygen tetrahedra linked into chains. Chain topology distinguishes inosilicates from the sheets of phyllosilicates.
Octahedral coordination: A coordination geometry in which a central atom is surrounded by six neighboring atoms or ions. Metal cations commonly occupy octahedral sites in phyllosilicate sheets.
Interlayer cation: A positively charged ion located between negatively charged layers in a layered mineral. Interlayer cations balance sheet charge and influence layer spacing.

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