A trioctahedral member of the true mica group. The end-member formula is KFe2+3Fe3+Si3O10(OH)2 and the known polytype is 1M. The ferri-iron component is found in the tetrahedral site. Tetra-ferri-annite is commonly associated with stilpnomelane. Stilpnomelane, when coexisting with tetra-ferri-annite, often appears to be replaced by tetra-ferri-annite. Therefore, tetra-ferri-annite occurs in very low-grade metamorphosed iron formations.
A trioctahedral member of the true mica group. The end-member formula is KMg3Fe3+Si3O10(OH)2, and the occurrence of tetra-ferriphlogopite is from Al-poor, ultrabasic magmas under oxidizing (typically late-stage) environments, such as in alkaline-carbonatites and in some mica kimberlites. Tetra-ferriphlogopite occurs as a 1M polytype.
See calcium silicate hydrate (CSH).
Inappropriate usage for a tetrahedral sheet.
See tetrahedral sheet
A tetrahedral sheet contains continuous two-dimensional corner-sharing coordination tetrahedra involving three corners and the fourth corner pointing in any direction. The tetrahedral sheet generally has a composition of T2O5 (T = Si, Al, Fe3+, Be, B…). After Guggenheim et al. (2006); see also references therein.
Cf., octahedral sheet
An invalid term, previously used as a classification of the micas where the number of silicon atoms per formula unit is four per four tetrahedral sites, see Rieder et al. (1998).
Cf., mica, true mica, brittle mica, interlayer-deficient mica, group names
The recording of the change in temperature and/or mass of a material when heated.
Rate of heat flow through a material. Heat flow is given as a unit of cross sectional area, per unit of temperature and time along the direction of heat flow.
The change in volume of a material with increase in temperature. It is often expressed as the coefficient of thermal expansion, which is the degree of expansion divided by the change in temperature.
A clay treated by heating (to dehydroxylation temperatures) to increase reactivity (e.g., as a preparation step to form geopolymers). During thermal activation, the clay minerals (partly) dehydroxylate resulting in distorted structures with broken bonds, which increases reactivity.
Syn., metaclay.
Cf., activated clay, firing