Zinc sulfide

Zinc sulfide occurs as two polymorphs, cubic sphalerite, and hexagonal wurtzite. Sphalerite is the stable phase at low temperatures and is a fairly common trace mineral in sulfidic sediments. It forms as a discrete solid phase since Zn is not incorporated to any significant extent within sedimentary pyrite (Luther et al., 1980, Morse, 1994). However, the initial precipitate in low-temperature aqueous solutions is often a mixture of nanoparticulate sphalerite and wurtzite. This is surprising since wurtzite is only stable with respect to sphalerite at high temperatures (>900 °C). Luther et al. (1999b) cited unpublished work by Rickard that showed that wurtzite never forms without sphalerite, but sphalerite can form as a discrete phase. The nature of the product appears to be pH-dependent, which is consistent with the formation of wurtzite and sphalerite being related to the structures of the dominant ZnS aqueous clusters. The wurtzite inverts slowly to sphalerite, which may take geological periods. Indeed, wurtzite interlayers have been observed in approx. 400 Ma old sphalerites (Rickard, 1983; Lindblom, 1986). Zinc forms anionic complexes in sulfidic sediment waters (e.g., Landing and Lewis, 1992). The speciation of Zn–sulfide complexes has been widely discussed because the measured solubility of Zn(II) in solution in equilibrium with ZnS is far better than can be accounted for by the simple Zn aqua ion. The problem, as noted by Dyrssen (1991), Hayashi et al. (1990), and Tossell and Vaughan (1993), is that the solubility data do not provide a unique solution to the speciation. In particular, the number of H2O and OH species cannot be determined. For example, the solubility data can equally well be fitted by species such as [Zn(SH)3(OH)]−2, [ZnS(SH)2(OH2)]2−, and [ZnS(SH)2]2−. Tossell and Vaughan (1993) used computational methods to show that [Zn(HS)3]− and [Zn(HS)3(OH)]2− would be energetically more stable. Daskalakis and Helz (1993) subsequently modeled solubility data with [Zn(HS)4]2−, [Zn(HS)]−, and [ZnS(HS)2]2−. If you are looking for high quality, high purity, and cost-effective zinc sulfide, or if you require the latest price of zinc sulfide, please feel free to email contact mis-asia.