Sulfur is the fifteenth most abundant element in the continental crust of the Earth (260 ppm), and the sixth most abundant element in seawater (885 ppm). Sulfur (atomic number 16) has the ground-state electronic structure [Ne]3s23p4, and is the first of the group VIB elements in the periodic table (S, Se, Te, Po). In minerals, sulfur can occur in the formal valence states S2−, S0, S4+, and S6+, corresponding to the sulfide minerals, native sulfur, the sulfite minerals, and the sulfate minerals. In the sulfide minerals,...