claymineral

Claymineral refers to a group of hydrous aluminum silicate minerals that form fine, plate-like sheets and are major constituents of soils, clays, and sediments. They are characterized by layered phyllosilicate structures and include several common types such as kaolinite, illite, smectite (montmorillonite), and chlorite. These minerals influence soil properties, hydraulic behavior, and geochemical processes in the environment.

The structure of clay minerals is based on tetrahedral sheets of silica (SiO4) alternating with octahedral sheets of aluminum, magnesium, or iron. In 1:1 clays, one tetrahedral sheet pairs with one octahedral sheet to form a single layer; in 2:1 clays, an octahedral sheet sits between two tetrahedral sheets. Isomorphic substitutions within the layers generate a negative charge that is balanced by exchangeable cations in the interlayer spaces. This charge and the ability of interlayer water to enter or leave the structure give rise to differences in swelling and cation-exchange capacity: 1:1 clays like kaolinite are typically non-swelling with low cation exchange, while 2:1 clays like smectites show considerable swelling and higher exchange capacity. Illite has potassium fixed in the interlayer, limiting swelling, and chlorite contains a brucite-like layer that also reduces swelling.

Clay minerals form through weathering and alteration of silicate minerals at low to moderate temperatures and are widespread in soils, sediments, and lake or marine environments. They are identified by X-ray diffraction and spectroscopy and influence soil fertility, water retention, and contaminant adsorption. In industry, clays are used in ceramics, drilling fluids, catalysts, adsorbents, and waste containment barriers, reflecting their diverse physical and chemical properties.