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.

See microfabric, clay.

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

See slaking.

The breakdown of large soil or clay material aggregates (typically >2-5 mm) or fine-grained sedimentary rock rich in clay into small particles (<0.25 mm) when rapidly immersed in water. Slaking occurs when aggregates are not sufficiently strong to withstand internal stresses caused by rapid water uptake into the pore structure or fabric of the aggregate. Internal stresses result from differential swelling of clay particles, trapped and escaping air from pores, rapid release of heat during wetting, and the mechanical action of moving water. Slaking is influenced by the presence of smectitic clays (either smectite, especially Na-montmorillonite, or interstratified clay with a smectite component) that shrink when dry and swell when wet. Organic matter often reduces slaking by binding the particles or by slowing the rate of surface wetting.