Refers to phyllosilicate minerals and to minerals which impart plasticity to clay and which harden upon drying or firing. This definition expands the previous definition of Brindley and Pedro (1972) by relating clay minerals to the properties of clays. Clay minerals may be of any crystallite size so that the term “clay mineral” is consistent with the definition of “mineral”, which is unrelated to crystallite size. (Quot Guggenheim and Martin, 1995). However, the unique properties of clays are partly related to their small particle size and high surface area (Guggenheim and Martin, 1996).
Cf., clay, phyllosilicate, mineral

A nanocomposite (i.e., fine-particulate material that is heterogeneous at the nanoscale level, at less than 10^-7 meters) where one or more of the constituent fine-particulate materials are clay minerals. Other parts of the composite may be, for example, polymers, which act as the dispersant. Some clay composites are fabricated with the polymer both around the clay particle and in the interlayer between the 2:1 or 1:1 layers.
Cf., nanocomposite

In geology, slickenside is a field term for striated and polished surfaces on a fault plane, which can often indicate the direction of fault movement. A clay slickenside is where the groundmass constituents, mostly clay, have been rearranged so that the platy particulates parallel the surface. In clay science, the term “slickenside” is used also for the natural crack surfaces that are polished, but produced by swelling and shrinkage in smectite-rich soils. In soil science, clay slickensides are a diagnostic feature of Vertisols, which are clayey high shrink/swell soils. The shrink/swell action “inverts” or mixes the upper parts of the soil because organic-rich surface material falls into cracks during dry periods.

An indurated, fine-grained sedimentary rock composed of >66% clay-sized constituents with lamination (stratification of <10 mm thickness), after Potter et al. (2005). See clay, claystone, mud, mudrock, mudshale, mudstone, silt, siltstone.

A fine-grained sedimentary rock having >66% clay-size constituents and little or no sand, with stratification (i.e., bedding) of >10 mm thickness. Bedding within the claystone may be massive (after Potter et al., 2005).
See clay, clayshale, mud, mudrock, mudshale, mudstone, silt, siltstone.

The tendency of a crystal to break along certain (and generally smooth) planes of weakness. Planes of weakness in a crystal usually reflect either the presence of a plane of weaker or fewer bonds in a structure, and thus cleavage is a diagnostic property. These planes can be described as Miller indices, and are thus rational.
Cf., parting

An obsolete term for margarite.

a) Clinker, in materials science, is a sinter product of limestone and clay (or other secondary raw materials such as fly ash, sand, or slag) heated in kilns. Clinker is used as the primary component for Portland cement and is typically composed of calcium silicate (CS) phases such as “alite” (Ca₃SiO₅, “C₃S”), “belite” (Ca₂SiO₄, “C₂S”), or “celite” (Ca₃Al₂O₆, “C₃A”).

b) Clinker, in geological sciences, refers to a sedimentary bed that has undergone combustion, such as a coal bed that has undergone combustion and alteration by an igneous intrusion or by a coal-bed fire. Clinker may also refer to a pyroclastic or lava mass that resembles furnace slag.
Cf., calcium silicate phases; fly ash; slag, blast-furnace; kiln, rotary; Portland cement.

The trioctahedral Mg-rich member of the chlorite group.
See chlorite

A monoclinic (P2,sub>1/c) polymorph of enstatite. It is a product of fast cooled protoenstatite. Clinoenstatite occurs in Mg-rich basaltic rocks.