silicati

Silicati, or silicates, are the largest and most diverse class of minerals in Earth’s crust. They are compounds built mainly from silicon and oxygen, often with additional elements such as aluminum, iron, calcium, magnesium, potassium and sodium. The key structural unit is the silicon-oxygen tetrahedron, SiO4^4−, in which silicon is surrounded by four oxygens. Tetrahedra link to one another by sharing oxygen atoms, producing a wide range of structures from isolated units to extensive three-dimensional frameworks.

Silicate minerals are commonly categorized by the degree of polymerization of their tetrahedra. Nesosilicates consist of isolated SiO4 tetrahedra (examples: olivine and garnet). Sorosilicates have paired tetrahedra (epidote, zoisite). Cyclosilicates feature ring-like arrangements of tetrahedra (beryl, tourmaline). Inosilicates form single chains (pyroxenes) or double chains (amphiboles). Phyllosilicates build sheet structures (micas, clays, chlorite). Tectosilicates compose three-dimensional frameworks (quartz and the feldspars).

Silicati are highly abundant in the Earth's crust and mantle, formed through magmatic crystallization, metamorphism and hydrothermal processes. They include economically important minerals and materials: quartz and feldspar are central to glass and ceramics; clays and micas have broad industrial uses; silica minerals contribute to construction materials such as cement and aggregates, and to many science and technology applications.

Health and environmental aspects are relevant in handling silicates. Inhalation of crystalline silica dust can cause lung diseases such as silicosis, so mining, processing and manufacturing require protective measures and exposure controls.