argilas

Argilas are a group of fine-grained natural materials dominated by clay minerals. They are typically finer than silt, with particle sizes less than about 4 micrometers, and they form cohesive, plastic masses when wet. Their microstructure consists of plate-like crystals that grant high surface area and unique adsorption properties.

Most argilas contain a mixture of minerals such as kaolinite, illite, and smectite (montmorillonite), along with minor quantities of chlorite, vermiculite, quartz, and feldspars. The particular mineralogy controls properties such as plasticity, cohesion, shrink-swell behavior, and cation exchange capacity.

Argilas form through weathering of silicate rocks or through deposition and diagenesis in sedimentary environments. They can be residual clays formed in place or transported clays derived from weathered rock, often accumulating in low-energy settings such as lakes, floodplains, or marine basins.

In soils, argilas influence texture, structure, drainage, and nutrient retention. Their high cation exchange capacity allows them to hold essential nutrients for plants but can also lead to poor drainage and aeration in highly clayey soils. Water content, drying, and heating alter their plasticity and strength.

Industrially, argilas are valued for ceramics, bricks, tiles, and porcelain; refined clays are used in drilling fluids, paper, cosmetics, and as adsorbents. Processing typically includes mining, drying, grinding, beneficiation, and sometimes calcination to enhance fire resistance or purity.

Global deposits are widespread, with major reserves in China, the United States, Brazil, India, and parts of Europe and Africa. The term argila is common in Portuguese and other Romance languages; in science, the minerals are referred to as clay minerals within the broader category of clays.