See astrophyllite group.

Laponite is a synthetic clay mineral with a hectorite-like composition, Na_0.7Si₈Mg_5.5Li_0.3O₂₀(OH)₄, and structure. Laponite is manufactured by BYK Additives & Instruments to modify the rheology of aqueous fluids. Laponite-S482 is a common excipient in pharmaceuticals.

Syenite (an igneous rock) dominated by anorthoclase with iridescent colors.

An obsolete name for a poorly defined material from Haute-Loire, France, possibly palygorskite-sepiolite.

A collection of equivalent points (i.e., identipoints) which are distributed periodically in space, and this term, in three dimensional space, commonly refers to Bravais lattices. From Guggenheim et al. (2006) and references therein. The term “layer lattice” is incorrect because it implies a structure rather than a lattice.
Cf., array, Bravais lattice, identipoint, structure

A lattice misfit is where there are (one or more) dimensional mismatches between a substrate crystal and an overgrowth crystal that has formed by heterogeneous nucleation. A lattice misfit parameter, d, may be calculated from d = D_a/a, where a is the lattice parameter of the (stress-free) substrate crystal, and D_a is the difference in lattice parameters between the underlying substrate and the overgrowth precipitate.
Cf., epitaxy, lattice

See cell parameters.

See zeolite.

For phyllosilicates, a layer (see Fig. 1) contains one or more tetrahedral sheets and an octahedral sheet. There are two types of layers, depending on the ratios of the component sheets: a “1:1 layer” has one tetrahedral sheet and one octahedral sheet, whereas a “2:1 layer” has an octahedral sheet between two opposing tetrahedral sheets. Quot Guggenheim et al. (2006).
See references therein.
Cf., plane, sheet, tetrahedral sheet, octahedral sheet

In phyllosilicates, the “layer charge”, “net layer charge”, or “permanent layer charge” is the total negative charge deviation from an ideal, unsubstituted dioctahedral or trioctahedral composition. In addition, phyllosilicates may have other charge effects on their surface, commonly referred to as the “variable layer charge”. For example, for an R³⁺-rich dioctahedral 2:1 layer, the layer composition is ideally: R₂Si₄O₁₀(OH)₂. In muscovite mica where R = Al and there is an Al substituted Si site, the layer composition is: Al₂(Si₃Al)O₁₀(OH)₂ and because an Al³⁺ substitutes for an Si⁴⁺, there is an unsatisfied residual charge on the layer that results, a layer charge of -1. In muscovite, this residual charge is compensated by an interlayer cation, K⁺, so that the structure is charge neutral. Because of the anion framework of O₁₀(OH)₂, layer charges are always negative, but may be reported in the literature as either a positive or a negative value. A negative layer charge results from either a solid solution where a cation of lesser positive charge substitutes for a cation of greater charge or by a vacancy (no charge) substitution for a cation. Anion substitutions [e.g., O for (OH)] are also possible but uncommon. The location and size of the substitution has a profound effect on the physical properties of clays. The layer charge is used in the classification scheme for phyllosilicates. The variable layer charge depends on the pH of the suspension. Assuming a simple pK model, low pH values lead to protonation of the surface species OH⁰ group located at the edges or the surface and hence, to a positive variable layer charge of OH₂⁺. Increasing pH values may lead to deprotonation and hence, to a negative variable charge of O^–. The pH point where the net charge of the entire particle is zero (e.g., for a clay mineral, the positive variable change is equal to the negative permanent charge) is called “point of zero charge” (pzc).
See point of zero charge.