A polymorph of quartz, has lower symmetry than quartz (I2/a) and a triclinic superstructure commonly occurs. The structure was described by Miehe and Graetsch (1992) as comprised of sections of right- and left-handed quartz alternating at the unit cell level to form a framework of corner sharing tetrahedra. The framework has 4-, 6- and 8-fold rings, and there is no open tunnel as found in alpha quartz. The nanoscale alternation follows the Brazil twin law, but because it is periodic at the unit cell level, moganite represents a (metastable) mineral phase. Moganite occurs as intergrowths with (alpha) quartz in chert, quartzine, flint, and chalcedony, thus indicating that these latter varieties are not minerals, but rock names. Any H₂O present in moganite is not structurally required.