argillosi

Argillosi is a term used in geology and soil science to describe materials whose primary constituent is clay minerals, broadly corresponding to what in English is called argillaceous or clayey. In Italian usage, argillosi can refer to soils, sediments, or rocks with a substantial clay fraction, typically finer than silt.

Argillosi are characteristically fine-grained, with most particles smaller than about 4 micrometers. They are rich in clay minerals such as illite, smectite, kaolinite, and chlorite, and often contain varying amounts of quartz, feldspar, and organic matter. The high specific surface area of clays gives argillosi soils high plasticity and cohesiveness when wet, and a tendency to shrink and swell with moisture changes. They generally exhibit low hydraulic conductivity and high water retention, influencing drainage, nutrient availability, and stability.

Formation and occurrence: Argillosi develop through weathering and chemical alteration of silicate minerals, followed by deposition in low-energy environments such as floodplains, lakes, or deep marine settings. Lithified versions form argillaceous rocks, including shale and mudstone, which can act as seals in sedimentary basins.

Significance and applications: In engineering, argillosi soils pose challenges for foundations and earthworks due to swelling and softening when wet. In agriculture, they impact crop growth through drainage and nutrient dynamics. In geology and hydrocarbon exploration, argillaceous rocks can serve as reservoirs or, more commonly, as impermeable barriers that influence fluid flow.

See also: argillaceous rocks; shale; mudstone; clay.