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.

See mirror plane.

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.

See system.

See system