A mathematical expression that describes how a spherical particle, nominally less than 20 micrometers, settles in a viscous fluid. This equation is used in clay science, although clay particles are generally flat plates and not spherical, and thus fall at slower velocities than spheres of equal density as calculated using Stokes’ law.
Cf., equivalent spherical diameter

An obsolete local name for a mixture of smectite and a Ca-rich phase(?), or Ca-montmorillonite, from Stolpen, Saxony, Germany.

Plural of stratum.
See stratum.

A layer of sediment or sedimentary rock (pl. strata).

A process describing how a clay or soil experiences different loading or unloading conditions in the past. The maximum past effective stress is generally determined experimentally by measurement of one-dimensional elastic and plastic deformation that occurs during consolidation, or one-dimensional stress-strain compression curves, or from known events, such as specific sea-level changes, groundwater table fluctuations, etc. Usually, stress history is used in combination with overconsolidation or overconsolidation ratio.
Cf., overconsolidation, overconsolidation ratio

The graphical representation of the loading or unloading processes that a clay has experienced in a triaxial stress condition. The stress path is usually plotted in the coordinate system of mean effective stress and shear stress. The mean effective stress is the average of the vertical and horizontal effective normal stresses, whereas the shear stress is the difference between the vertical and horizontal effective normal stresses.

An obsolete term for an iron-rich chlorite from Striegau, Silesia (now Poland).

See hollandite.

The accepted atomic, ionic, and molecular arrangement of atoms of a material. (Quot Guggenheim et al., 2006)

A structured clay is a clay that exhibits stiffened or strengthened behavior, usually caused by microstructure features, such as cementation, aggregation, ageing, or flocculation. Usually, a structured clay exhibits a higher yield stress, Young’s modulus, and failure strength than a non-structured clay. Re-sedimentation of the same material in the laboratory usually destroys the in-situ structure formed in the natural, non-processed clay.