Atomic Positional Parameters
Hg 3a 0.7198 0.0000 0.6667
S  3b 0.4889 0.0000 0.1667

Reference
P Auvrey and F Genet (1973) Bulletin de la Societe Francaise de Mineralogie et de Cristallographie, 96, 218

Mineral Chemistry
Cinnabar is the mercury sulfide mineral stable at ambient temperatures. Transformation to metacinnabar, the cubic form of HgS, occurs between 588 and 618 K.

The CHIME figure shows cinnabar, with mercury atoms coloured vermillion, and sulphurs yellow. The unit cell is outlined. Note the unusual coordination of the mercury in the crystal structure.