An organoclay with at least one dimension in the micrometer range dispersed in a polymer.
Cf., organoclay, organoclay nanocomposite

Clay microfabric is the description of the spatial distribution of clay particles in either clay-rich rock or sediment, commonly observed directly by electron microscopy of aggregates, domains, or layer stacking effects within the material. Microfabric variations may affect physical properties, conditions of formation, and evolution of the material. See Bennett et al. (1977) and Potter et al. (2005) and see microstructure. Types of clay microfabric are (after Grabowska-Olszewska et al., 1984):

– domain microfabric : A domain microfabric is composed of unoriented, coarse domains of kaolinite crystals with parallel axial orientation. Domain boundaries involve face-to- edge and edge-to-edge particles. Pore shapes are complex, with equidimensional interdomain pores (2-8 μm in diameter) and smaller fissure-like intradomain pores (<0.5 μm). This microfabric is characteristic of eluvial kaolinitic clays; domains often form from weathered feldspar crystals. - honeycomb microfabric : Honeycomb microfabric consisting of unoriented, high porosity (60- 90%), nearly equidimensional cells or domains commonly 2 – 12 μm in size in sedimentary clay-rich soils. Cell walls are comprised of microaggregates of face-to- face and face-to-edge clay particles of montmorillonite-illite mineralogy. Silt/sand grains are rare and are distributed throughout the soil. Most cell contacts are of flocculation type (clumping of small particles), which promotes the high porosity. The fabric is syngenetic (i.e., formed during sedimentation) and forms in recent marine and lacustrine sediments.

– laminar microfabric : A sedimentary clay soil with a laminar-flow appearance from well developed bedding/sorting of its structural components, mostly microaggregates with face-to-face, and occasional face-to-edge, boundaries. Pores between aggregates are fissure- and wedge-shaped parallel to the lamination. This microfabric is common of clay-rich deposits (>50%) of varying mineral composition and forms in syngenetic and/or post-depositional environments.

– matrix microfabric : A microfabric characterized by a continuous unoriented clay matrix with a non-uniform distribution of silt/sand grains. The clay (illitic and mixed-layer particles) forms microaggregates with face-to-face, face-to-edge, and edge-to-edge boundaries. Pore sizes range from 8 to 2 μm for poorly compacted and compacted sediment/soil respectively. Formation can be syngenetic and/or post-depositional.

– pseudoglobular microfabric : Pseudoglobular microfabric is formed by the weathering of iron-rich igneous or metamorphic rocks with neoformation of iron phyllosilicates (e.g., nontronite). This microfabric contains spheroidal microaggregates ranging in diameter of 5 – 20 μm, sometimes composed of sheet-like particles with face-to-edge contacts or with face-to-face and face-to-edge interactions. Porosity is made of equidimensional interglobular (10 – 15 μm) and equidimensional or elongate intraglobular voids.

– skeletal microfabric : Skeletal microfabric is comprised of a generally uniform, porous structure of unoriented silt/sand grains (to 60%) and clay (10 – 30%), the latter forming a discontinuous matrix and commonly accumulating along the larger-grain boundaries to tenuously bond the grains together. This microfabric is more compact than the honeycomb microfabric with porosities ranging from 40 – 60%. The skeletal microfabric occurs more commonly in recent clay deposits of varying mineral composition (but often illitic). Formation can be syngenetic and/or post-depositional.

– sponge microfabric : Sponge microfabric consists of coarse aggregates (> 80 μm in diameter) of sheet-like microaggregates with mostly face-to-edge and face-to-face contacts, forming a continuous fine-cellular network resembling sponge. The clay material is not orientated and pores are irregular in shape and < 3 μm in size. For example, this microfabric has been reported in smectite clays of hydrothermal origin. See microfabric, microstructure - turbulent microfabric : A microfabric with a turbulent-flow appearance derived from clay microaggregates that are well oriented along deformed laminations of clay-coated silt/sand grains within a matrix of deformed bedded clay. Clay microaggregates are bounded by face-to-face clay particles, and locally, by face-to-edge contacts at very small angles. The clay content is > 20%. The pores are primarily fissure-like and elongated along the lamination. This microfabric is commonly formed during the diagenesis (compaction) of clay sediments with precursors of honeycomb and matrix microfabrics.

An obsolete term for lepidolite.

An International System (SI) unit of measure equal to 10^-6 meters.

An old name for micrometer.

A general term for dietary essential nutrients required in relatively small amounts (less than 50 milligrams per day). For example, micronutrients include vitamins (organic compounds) and trace elements (e.g., Fe, Cu, Zn, I, Se, Mn, Mo, Cr, F, Co) for human consumption that may be potentially provided by ingestion of clays, whereas clays in soils provide these nutrients for plants.
Cf., macronutrient

In clay science, micropores (Figure 3) are cavities with diameters of <2 nm within a sample, following the IUPAC convention (Rouquerol et al., 1996), which is also similar in size to a common (upper) clay particle size used in clay studies. Thus, these pores are probably present at the edges of single stacks of unit structures and at widened edges of the interlayer. In soil science, micropores are defined as 5 - 30 μm, ultramicropores are 0.1 – 5 μm, and cryptopores are <0.1 μm (Soil Science Society of America, 1997). The pore volume distribution of clays is commonly determined by gas adsorption methods (typically H₂O, N₂ or, CO₂).
Cf., macropore, mesopore

In clay science and materials science, microstrain is a local strain caused by a local deviation of the lattice parameters from the mean value. Microstrain originates by 1) atomic substitutions where the ionic radius of the substituting ion differs from the original ion, 2) missing atoms or ions in the structure, 3) interactions with neighboring crystallites having slightly different lattice parameters, e.g., owing to twinning, an inhomogeneous mixture of crystallites with similar lattice parameters. In X-ray diffraction patterns, microstrain causes peak broadening. A microstrain expression is defined as the root-mean-square of the lattice parameters. In physics, mechanics, and many engineering disciplines, microstrain is a strain expressed in terms of parts per million (10^-6), where strain is defined as a ratio of the change in the distance/dimension to the original distance/dimension, and hence it has no unit and is dimensionless.

An obsolete term for a Cr-bearing kaolinite.

See reyerite group.