# Rhombohedral crystal system

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In crystallography, the rhombohedral (or trigonal) crystal system is one of the 7 lattice point groups. A crystal system is described by three basis vectors. In the rhombohedral system, the crystal is described by vectors of equal length, all three of which are not mutually orthogonal. The rhombohedral system can be thought of as the cubic system stretched along a body diagonal. a=b=c; alpha=beta=gamma unequal to 90°. In some classification systems, the rhombohedral system is grouped into a larger hexagonal system.

There exists only one rhombohedral Bravais lattice.

The point groups that fall under this crystal system are listed below, followed by their representations in international notation and Schoenflies notation, and example crystals.

 name international Schoenflies example rhombohedral holohedral $\overline{3}m$ D3d calcite rhombohedral hemimorphic $3m$ C3v tourmaline rhombohedral tetartohedral $\overline{3}$ S6 dolomite trapezohedral 32 D3 quartz rhombohedral tetartohedral $3$ C3
de:Rhomboedrisches Kristallsystem