Is used to describe an object with a systematic repetition of features, and is particularly useful to describe crystal shapes or atom locations in an object.

Material formed contemporaneously with rocks that are associated or enclose material.

A geometrically fixed intergrowth between two phases. Originally defined as between two polymorphs only and extended to include an oriented intergrowth between any two phases.
Cf., epitaxy, topotaxy

A region of space within the universe. Systems are considered in thermodynamic or other studies to determine how a change in the environment (e.g., temperature changes, pressure changes, etc.) will affect the system. Systems may be closed by encapsulating in noble metals, placing a liquid in a sealed beaker, etc. A “closed system” is affected only by receiving energy from or giving energy to the outside environment. An “open system” differs from a closed system by an exchange of matter, in addition to energy. An “isolated system” receives neither matter nor energy across the boundary.

See system

In the context of polymer/clay nanocomposites, a tactoid is any collection of “primary” (i.e., the smallest division of the phyllosilicate particle that retains the chemical character of the compound, either a 1:1 or 2:1 layer), colloidal-size clay particles, which are essentially acting as a unit.

An obsolete term for tainiolite.

See gangue.

A trioctahedral member of the true mica group. The end-member formula is KLiMg₂Si₄O₁₀F₂, and tainiolite occurs as 1M, 2M₁, and 3T polytypes. Tainiolite is found in alkaline and peralkaline rocks, especially syenites and metasomatites.
Syn., taeniolite

See birnessite.