crystal-systems-gemstones-gemmology-roragems The gems are sorted by their crystal system: cubic (isometric), tetragonal, hexagonal, trigonal, orthorhombic, monoclinic, and triclinic. 11/04/2020 1200 × 500 GEMSTONE CRYSTAL SYSTEMS The gems are sorted by their crystal system: cubic (isometric), tetragonal, hexagonal, trigonal, orthorhombic, monoclinic, and triclinic.