Crystal system
From Online Dictionary of Crystallography
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Système cristallin (Fr); Kristallsystem (Ge); Sistema cristalino (Sp); Sistema cristallino (It); Сингония (Ru); 晶系 (Ja)
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 the same crystal system which intersect exactly the same set of Bravais flocks.
Crystal systems in two and three dimensions
In the two-dimensional space there exist four crystal systems:
- oblique
- rectangular
- square
- hexagonal
In the 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
Section 1.3.4.4.3 in of International Tables of Crystallography, Volume A, 6th edition