Crystal system

Système cristallin (Fr). Kristallsystem (Ge). Sistema cristallino (It). 晶系 (Ja). Сингония (Ru). Sistema cristalino (Sp).

Definition

A crystal-class system, or crystal system for short, contains complete geometric crystal classes of space groups. All those geometric crystal classes belong to the same crystal system which intersect exactly the same set of Bravais classes.

Crystal systems in two and three dimensions

In two-dimensional space there exist four crystal systems:

• oblique
• rectangular
• square
• hexagonal

In three-dimensional space there exist seven crystal systems:

• triclinic
• monoclinic
• orthorhombic
• tetragonal
• trigonal
• hexagonal
• cubic

Note that the adjective rhombohedral refers to a lattice system, not to a crystal system. Rhombohedral crystals belong to the trigonal crystal system, but trigonal crystals may belong to the rhombohedral or to the hexagonal lattice system.

See also

• Lattice system
• Chapter 1.3.4.4.3 of International Tables for Crystallography, Volume A, 6th edition