Clay mineral

A fine-grained mineral, usually a sheet silicate, that forms clay-sized particles and commonly develops through rock weathering or sedimentation.

Phyllosilicate: A silicate mineral whose tetrahedral sheets are linked to octahedral sheets. Most clay minerals belong to this broad structural family.
Chemical weathering: The decomposition or alteration of minerals through chemical reactions at or near Earth's surface. It transforms primary rock-forming minerals into many secondary clay minerals.
Kaolinite: A non-expanding 1:1 layer silicate with one silica sheet bonded to one alumina sheet. Its tightly hydrogen-bonded layers contrast with expandable clay minerals.
Soil fertility: The capacity of soil to support plant growth by supplying nutrients and suitable conditions. Clay surfaces retain nutrient cations that plants can access through soil water.
Clay: A natural fine-grained earth material composed of clay minerals and often other constituents. Clay is a material or particle-size category, whereas a clay mineral is a mineral species or group.
Silicate mineral: A mineral built from silicon–oxygen tetrahedra, alone or linked into larger structures. Clay-mineral crystal frameworks are built from linked silicon–oxygen units.
Hydrolysis: A chemical reaction in which water participates in breaking or forming chemical bonds. Hydrolysis of silicates contributes to clay-mineral formation during weathering.
Smectite: A group of expandable 2:1 layer silicates with substantial interlayer water and exchangeable cations. Smectites demonstrate how interlayer access produces swelling and high exchange capacity.
Bentonite: A clay-rich rock, commonly dominated by smectite, formed largely from altered volcanic ash. Its swelling and binding properties make it useful in drilling fluids and liners.
Silt: A sediment particle-size class intermediate between clay and sand. Silt can be clay-sized in appearance but is defined by larger particle diameters.

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