Characteristic features of crystal chemistry of natural mercury-containing sulfides and sulfosalts

Many mercury-containing minerals belonging to the class of sulfides and sulfosalts are based on a highly symmetric sphalerite type structure (ZnS), where both components occupy sites with high point symmetry providing stable orientation of directed interatomic interactions. Some structures of natural compounds of this type are used to demonstrate that the geometric matrix of cations and anions tends to be preserved during variation of the chemical composition caused by migration of elements under natural conditions. The fundamental laws of crystal formation are confirmed: the governing role of the families of close packed (crystallographic) planes, the independence of ordering of different types of atoms, the tendency of sulfur atoms to mirror plane symmetry, and the trend to cluster formation in the development of crystal structures, as exemplified by [As(4)S(12)](12-), [(Cs,Tl)S(12)](23-), [Tl(2)S(12)](22-) atomic groups.