Hydrothermal deposits are associated with volcanic activity and hot springs. Metal cations are transported by soluble Cl- complexes at high temperature. Ag and AgS, Au. Sedimentary Environments Sulfides also may form in sediments under the reducing conditions resulting from decaying organic matter. Bonding and Crystal Chemistry Bonding in sulfide minerals is typically less ionic than in oxides and, consequently, Pauling's rules often fail.
Sulfide minerals have a restricted composition range and solid solution is rare.
The Fe atoms occur in six-fold coordination. If you have a good VRML viewer, here is a model of the pyrite FeS 2 structure. Marcasite Marcasite is an orthorhombic polymorph of pyrite and occurs in low-temperature sedimentary environments. Sphalerite, ZnS 2 Sphalerite is the primary ore mineral of zinc. The structure is very simple with Zn in tetrahedral coordination with sulfur.