See astrophyllite group.

A solid where the constituent components are randomly packed. Many variations can occur between the two extremes of crystalline vs. non-crystalline. For example, a non-crystalline material, such as many glasses, consists of atoms arranged as groups of tetrahedra or octahedra. However, although such groups have almost the same mutual arrangements, they are displaced without periodicity with respect to each other (i.e., limited order or short-range order). (Quot Guggenheim et al., 2006)
Cf., crystalline

Fe³⁺-bearing and dioctahedral member of the smectite group of minerals. A representative formula is: R0.33Fe3+2(Si3.67Al0.33)O10(OH)2^.nH₂O, where R refers to the exchangeable cation, commonly Na, Ca and Mg, and n is a rational number, not necessarily an integer. The layer charge originates by substitution primarily in the tetrahedral sheet. One of the dominant minerals along mid-ocean ridges.
Cf., smectite

A polymorph of Al(OH)₃ that occurs in bauxites and soils and rarely in dolomitic marls. Nordstrandite is a two-layer, dioctahedral structure of Al octahedra (similar to layers found in gibbsite), but with displacements between the layers. Ideally, adjacent layers are superposed in bayerite, offset in nordstrandite, and reversed in gibbsite, presumably because of strong polarization effects of the OH.
Cf., gibbsite, bayerite

The correlated motion of atoms in a molecule or crystal identified by a specific frequency and with the same phase relations in the vibrational spectrum. The symmetry of the normal mode is related to the symmetry of the molecule or crystal.
Cf., vibrational spectroscopy

The number of gram equivalent weights of the solute in one liter of solution. Useful where experiments use measured volumes and temperature effects are not being studied.
Cf., molarity, formality, molality, mole fraction

A clay mass that has been compressed by the stress expected from just overburden, without any previous overloading.
Cf., preconsolidation stress, overconsolidation ratio

A trioctahedral member of the true mica group. The end-member formula is KLiMn³⁺₂Si₄O₁₂. The chemical composition of norrishite is noteworthy because it is Li- and Mn-rich and anhydrous, oxygen-rich, and fluorine-poor content. Norrishite forms as the 1M polytype (space group C2/m), and the octahedral sites show Jahn-Teller distortions (Tyrna and Guggenheim, 1991). Norrishite occurs at the (now-filled) Hoskins manganese mine, near Grenfell, New South Wales, Australia.

Nsutite was originally described as one in a series of similar manganese oxide phases called “gamma MnO₂“. Zwicker et al. (1962) showed that the samples they studied have a chemical formula more typical of a hydrous component, e.g., Mn(O,OH)₂. S. Turner (1982), in a PhD. thesis (Arizona State University), as described in Post (1999), showed that the samples he studied are comprised of random intergrowths of pyrolusite (MnO₂) and ramsdellite (MnO₂) or a ramsdellite-like phase and, therefore, classification of nsutite as a mineral is questionable. Samples have numerous structural defects and grains commonly have crystallite boundaries. Large deposits occur near Nsuta, Ghana; it has been noted in marine nodules and as residual oxidation products of Mn-rich carbonates.
Cf., vernadite