Crystallography and Mineralogy. Each of the natural faces of a crystal. Also: (an imaginary plane corresponding to) a planar array of structures…

A pair of parallel faces, parallel to the vertical axis of the crystal in the triclinic system (in which two such pairs constitute a prism).

A pair of parallel and equal faces, parallel to the orthodiagonal in the monoclinic (or monosymmetrical) system (in which two such pairs…

A crystal form, shown by triclinic minerals, consisting of a single face bounded by other faces having no simple symmetrical relation to it (or to…