The removal of (OH)^– groups from the atomic structure of a phase. Decomposition/recrystallization usually results, but there are some materials that form dehydroxylate structures prior to recrystallization.
Cf., dehydroxylate, rehydroxylation

Delamination is a term used to describe a layer-separation process between the planar faces of adjacent layers of a particle. Delamination describes a process whereby intercalation occurs with the introduction of guest material and the stacking of layers remains. This term differs from exfoliation. Exfoliation implies that the orientation between the layers of the host structure is lost, and that interlayer cohesive forces are overcome. Where delamination or exfoliation cannot be distinguished, use “intercalation” or “delamination/exfoliation” to describe the process. See intercalation, exfoliation, 1:1 layers, 2:1 layers. (From AIPEA Nomenclature Committee, 2011, unpublished)

An obsolete term for a chlorite material, rich in ferric iron, probably a Mg-rich chamosite.

An approximate method of incorporating quantum mechanics in calculating the electronic structure and related properties of a finite or periodic molecular model. This method differs from ab initio methods (i.e., a first principles method typically using a molecular orbital model) in that electron-electron interactions are approximated using functional mathematics in vector space.
Cf., molecular dynamics, quantum calculation

In geology, sedimentary deposits (or eluvium) derived by weathering, either with or without significant movement by the effects of gravity. In soil science, a soil horizon developed by the removal of soil material in suspension or solution (leaching) from a layer of a soil.

See hydrotalcite group.

The deviator stress is the difference between the major principal stress (σ₁) and minor principal stress (σ₃). The deviator stress usually defines the shear resistance of a clayey soil under triaxial shear loading.

See astrophyllite group.

Crystallization from a glass.

An obsolete term for a mixture of poorly crystalline phyllosilicates (1:1 and 2:1 types). When red, “deweylite” was called “eisengymnite”, and when found at Bare Hills, Maryland, USA, “deweylite” was called “gymnite”.