A geometrically fixed intergrowth between a reactant and one or more of its products which resulted from a solid-state transformation. Different authors have suggested that the product phase(s) should maintain orientation a) of most atom positions or b) of symmetry axes of the reactant phase. c) The reaction involves conversion throughout a single crystal.
Cf., epitaxy, syntaxy

An obsolete varietal term for manganoan greenalite (or magnesian caryopilite).

A regular interstratification of dioctahedral chlorite-like layers and smectite-like layers in a ratio of 1:1. Tosudite must be dioctahedral on average, although tosudite may refer to smectite-like components that are of dioctahedral or trioctahedral character. Dioctahedral chlorite may be of the type di,dioctahedral or di,trioctahedral interstratified with either dioctahedral smectite-like or trioctahedral smectite-like layers. (Bailey, 1982; Frank-Kamenetskii et al., 1965).

Mineralogical term: an element found in small quantities in a mineral and not considered essential because it is not required for the structure to exist. A trace element is not quantitatively defined, but is generally considered to be <1wt. %. b) Medical/biological term: an element that occurs in animals or plants in small quantities and is required for physiological health. Cf., essential trace element

The phenomenon by which primary minerals in general, and chain silicates and phyllosilicates in particular, alter usually by weathering to secondary minerals through the direct incorporation and reuse of some part of the structure of the parent mineral. Products of transformation reactions are often pseudomorphous or alteromorphous after the primary reactant (parent) mineral, and often exhibit regular crystallographic and orientation relations with the reactant mineral.
See neoformation, inheritance

If an energetically unstable complex is present, TST states that a transitional state, or activated complex, occurs. This activated complex is a transitional state between the reactants and products, and is considered a hypothetical way to develop or explain the kinetics of, most commonly, a single-step (elementary) chemical reaction. The transitional state represents an energy barrier that must be overcome for mineral growth or dissolution.
Cf., molecularity

Describes a material that allows radiant energy to pass through it without significant adsorption, scatter or reflection.
Cf., opaque, translucent

A species of the chlorite mineral group that would have a trioctahedral 2:1 layer and a dioctahedral interlayer. There are no known chlorite structures of this type. Bailey (1988) described franklinfurnaceite, which has Ca between the 2:1 layer and the interlayer and thus is not a true chlorite, as tri,dioctahedral if the Ca is not considered.
Cf., dioctahedral chlorite, di,trioctahedral chlorite, trioctahedral chlorite, dioctahedral sheet, trioctahedral sheet

Tridymite, a high temperature polymorph of SiO₂, has many structural modifications and these are described by Heaney (1994). Ideally, the basic structure is comprised of sheets of hexagonal tetrahedral rings with alternate tetrahedra around a ring with apices pointing in opposite directions from adjacent tetrahedra. Adjacent tetrahedral sheets are related by a mirror plane to form channels normal to the sheets. Stacking of the sheets follow ABAB… stacking with A representing the initial sheet and B relating to its mirror image. Tridymite rarely occurs upon heating of SiO₂ without the presence of a flux. Tridymite occurs as a devitrification phase of obsidian.
Cf., cristobalite, quartz

A trioctahedral member of the true mica group. The formula is KLi_1.5Al_1.5AlSi₃O₁₀F₂. This formula does not represent an end-member composition. Trilithionite occurs in Li-rich, late stage, granitic pegmatites and aplites as 1M, 2M₁ and 3T polytypes.