Silver occurs in South China wolframite-quartz veins in three forms: (1) as micro inclusions of Ag
2S and AgBiS
2, (2) as argentite and matildite as a result of exsolution from galena and (3) as Ag-bearing sulfosalts and independent silver
minerals.
According to mineral assemblages the Ag-bearing tungsten deposits are classified as two types: (1) Ag-bearing W-Bi deposits
in eastern Nanling, where gustavite has been found and (2) Ag-bearing W-Sn(Sb) deposits which are mainly distributed in western
Nanling. The authors consider that the enrichment of silver and sulfosalt minerals in the lower parts of pneumato-hypothermal
tungsten deposits is the result of reversed vertical zoning caused by high concentrations of F and S in the ore-forming fluids.