Geochemical affinities chalcophile

Zinc (atomic no. 30) is a bluish-white, relatively soft metal with a density of 7.133 g cm . It has an atomic weight of 65.39, a melting point of 419.6 °C, and a boiling point of 907 °C. Zinc is divalent in all its compounds and is composed of five stable isotopes ( Zn = 49%) and a common radioisotope, Zn, with a half-life of 245 days. It belongs to group Ilb of the periodic table which classifies it as a heavy metal whose geochemical affinity is chalcophilic. 

Goldschmidt (32) also introduced the concept of a geochemical classification of elements, in which the elements are classified on the basis of their affinities and tendencies to occur in minerals of a single group. The chalcophile elements are those which commonly form sulfides. In addition to sulfur, they include Zn, Cd, Hg, Cu, Pb, As, Sb, Se, and others. When present in coals, these elements would be expected to occur, at least in part, in sulfide minerals. Sulfides other than pyrite and marcasite have been noted in coals, but, except in areas of local concentration, they occur in trace or minor amounts. 

Unlike silicon and germanium, tin and lead belong to the family of chalcophile elements (according to the Goldshmidt geochemical classification), which have a high affinity to sulfur. In this connection the stability of the stannathiane Sn—S bond (in the Sn—S—Sn... 

TABLE 2.1 A cosmochemical and geochemical classification of the elements based upon their Lithophile/siderophile/chalcophile affinities and their refractory or volatile character (after Palme and O Neill, 2003). ... 

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