A synthetic, poorly crystalline/amorphous SiO₂ product composed of spheres of <<1 m in diameter, and thus with a large specific surface area. Silica fume is a by-product of the Si and FeSi alloy production and used as an additive for concretes or geopolymers. Cf., cement, geopolymer

Lung fibrosis caused by the inhalation of dust containing crystalline silica (SiO2) in any of its forms (e.g., quartz, cristobalite, tridymite, coesite, stishovite).

A general term for any non-consolidated, clast-rich material that consists of >50% primary particles with diameters of 4-63 μm (American geologists), 2-63 μm (European geologists), or 2-50 μm (American soil scientists).
See siltstone

A sedimentary rock with primarily silt-size components; siltstone rocks may show sedimentary structures, such as flow structures and cross-bedding. Siltstones are often, but not always, chemically cemented.
See mud, mudstone, silt

Obsolete term for an iron-rich red clay used as a pre-history ocher in the Black sea region.

Bonding of powdered material by solid-state reactions at temperatures lower than melting.

Energy required to separate an ion an infinite distance from its equilibrium position in a crystal. In calculating an electrostatic site energy, the site energy is the sum of all the Coulombic and all the repulsive energies between the ion in the site and all neighbors in the unit cell.

See hydrotalcite group.

An obsolete term for glauconite.

A waste product from the iron-producing industry, sometimes used as a substitute for metaclay to produce geopolymers. Blast-furnace slag is produced when pure iron is separated from the silicate-containing byproducts. These byproducts are quenched rapidly in water to obtain a highly reactive material with a poorly crystalline to amorphous (glass-like) structure.
Cf., geopolymer, metaclay