A solid consisting of atoms, ions, or molecules packed together in a periodic arrangement. The material must have sufficient atomic ordering such that a (X-ray, electron, neutron, etc.) diffraction pattern containing well-defined maxima can be indexed using Miller indices (Nickel, 1995).
Cf., non-crystalline

An attempt to describe the state of crystallinity of a solid as a value of some characteristic, usually relating to diffraction. The term is a misnomer because it suggests that the complex idea of crystallinity may be represented by a single value. The use of the term “crystallinity index” should be avoided, although it may be placed within quotation marks when referring in a limited way to previously referenced work (Guggenheim et al., 2002). Some indices are useful to describe e.g., crystallite size or grade of diagenesis. Indices were derived by Hinckley (1963) to distinguish between different samples of kaolinite, by Kübler (1964) to describe certain origins of samples of illite, and by Árkai (1991) to describe different origins of chlorite. It is recommended to refer to the author describing the procedures necessary to define the value, regardless of what the index may actually be describing, such as the Hinckley index.
See Guggenheim et al. (2002) and references therein.
Cf., Árkai index, Kübler index, Hinckley index

A set of reference axes used in crystallography. These axes are usually three in number, although in some cases, they may be four. The axes are generally mutually perpendicular, coincide with symmetry axes or the normals to symmetry planes, and in cases where the crystal lacks symmetry, parallel to lines of intersection of two faces with greatest areas. These axes are designated as a, b, c, and angles between axes are designated α, β, and γ where α is located between axes b and c, β is located between axes a and c, etc. according to the right- hand rule.
See also: crystal system.

An obsolete name for altered material, probably vermiculite.

A pedofeature involving material (commonly oriented clay coatings, but also gels, amorphous, etc. coatings) that covers the surfaces of voids, grains, and aggregates, and are common in paleosols. Cutans may be derived and differentiated as diffusion cutans, illuviation cutans, and stress cutans. Other cutans may describe compositional variations. Cutans may be identified in a paleosol or soil under the optical microscope. See pedofeature :

– argillan : An (oriented) clay coating over grains, voids, or aggregates. Compositional characteristics may be used as prefex modifiers, as “ferri-argilan” (iron oxide stained) or “organo-argillan” (stained by organic matter). See cutan, pedofeature, ferran, mangan. Syn., clay skin.

– calcan : A cutan composed of calcite.

– ferran : A cutan of iron oxide and hydroxide

– mangan : A cutan of manganese oxide and hydroxide

– organan : A cutan composed of organic matter

– silan : A cutan formed of opal or chalcedony

– sesquan : A cutan composed of Al-Fe oxides

– soluan : A cutan of soluble salts (e.g. gypsum)

A poorly defined material, possibly muscovite and albite.