trigonalsystem
Trigonalsystem, in crystallography, is one of the seven crystal systems used to classify crystalline materials by symmetry. Crystals in this system exhibit threefold rotational symmetry around a principal axis, and may possess additional symmetry elements consistent with the space group.
Two lattice representations are used to describe trigonal crystals: a rhombohedral lattice and a hexagonal lattice.
Historically, the trigonal system has been discussed as including both rhombohedral and hexagonal forms; in modern
Representative minerals include calcite and dolomite, which crystallize in a trigonal lattice (rhombohedral). The trigonal system