Clayey

Clayey is an adjective used in geology and soil science to describe a material that contains a substantial proportion of clay minerals or exhibits the characteristics associated with clay. The term is commonly applied to soils with high clay content, as well as to rocks and sediments in which clay is a major component. It derives from clay and the suffix -ey, indicating resemblance or quality.

Clay minerals are extremely fine, typically under 0.002 millimeters in diameter, and have a sheet-like crystal structure that yields a large surface area. When wet, clayey materials become highly plastic and cohesive and can be shaped or molded; when dried, they lose plasticity and may become hard or brittle. They tend to retain water, have low permeability, and exhibit shrink–swelling behavior as moisture content changes. Mineralogy (for example, kaolinite, illite, smectite) influences plasticity and shrink-swell potential.

In soils, a clayey texture means clay is the dominant particle size fraction, often described within soil textural class names such as clay or clay loam. In geology, clayey compositions are common in mudstones, shales, and clay-rich matrices of various sedimentary rocks. In ceramics, the term describes raw clays that are sufficiently plastic for shaping and firing.

Overall, clayey describes a material with high clay content and the corresponding physical properties, which influence drainage, stability, and workability in agricultural, engineering, and artisanal contexts.