# Hexagonal crystal family

## Union of crystal groups with related structures and lattices / From Wikipedia, the free encyclopedia

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In crystallography, the **hexagonal crystal family** is one of the 6 crystal families, which includes two crystal systems (hexagonal and **trigonal**) and two lattice systems (hexagonal and **rhombohedral**). While commonly confused, the trigonal crystal system and the rhombohedral lattice system are not equivalent (see section crystal systems below).^{[1]} In particular, there are crystals that have trigonal symmetry but belong to the hexagonal lattice (such as α-quartz).

**More information**Crystal system, Lattice system ...

Crystal system | Trigonal | Hexagonal | |
---|---|---|---|

Lattice system | Rhombohedral |
Hexagonal | |

Example | Dolomite (white) |
α-Quartz |
Beryl |

The hexagonal crystal family consists of the 12 point groups such that at least one of their space groups has the hexagonal lattice as underlying lattice, and is the union of the hexagonal crystal system and the trigonal crystal system.^{[2]} There are 52 space groups associated with it, which are exactly those whose Bravais lattice is either hexagonal or rhombohedral.