Natural HgS nanoparticles in sulfide minerals from the Hetai goldfield

Nanomaterials may be of engineered or natural origin, the later being less known. Ores from many metal deposits contain high Hg concentrations, yet the chemical and structural composition of Hg-containing minerals is rarely investigated. Here, we studied pyrrhotite samples from the Hetai goldfield, Guangdong Province, China, by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Results reveal that the pyrrhotite contains Fe, S, Hg, Au, and Te, and that there is a high correlation between Hg and S, and Hg and Fe. Moreover, HgS nanoparticles and particle aggregates are incorporated into the pyrrhotite matrix. These nanoparticles varied in shape and size and were commonly crystalline, occurring in polycrystalline or distorted regions of the matrix. This is the first report on HgS nanoparticles accounting for the concentrations of Hg in ores from the Hetai goldfield. Overall, our findings disclose that some metal deposits are a major source of natural HgS nanoparticles.