trigonal system

trigonal system

[trī′gōn·əl ′sis·təm]
(crystallography)
A crystal system which is characterized by threefold symmetry, and which is usually considered as part of the hexagonal system since the lattice may be either hexagonal or rhombohedral.
References in periodicals archive ?
1 show that all the peaks coincide with those of calcite containing magnesium (Ca, Mg)CO3 (JCPDS 43-0697), which is indexed in the trigonal system with the R-3c space group (No.
This is Renault's trigonal system that is mounted on a sub frame away from the main body and insulates the interior from road noise.