Resistance to breaking or deforming a crystal.

The maximum stress developed in a material by a pulling load at the point of rupture, given as a load per cross sectional (e.g., kg per cm²).

An obsolete term for a clay of unknown composition resembling halloysite, from Haute-Loire, France.

Unglazed or glazed building blocks of either low- or high-fired clay, typically used as ornamental features on buildings.

A red glaze made from hematite.

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