Determination of silver-bearing minerals in the Lady Loretta ore.

The Queensland deposit averages 5.9% Pb, 17.1% Zn and 97 g/t Ag, mostly in fairly complex intergrowths of pyrite, sphalerite and galena. Average silver distribution from four pilot plants was 28% in the lead concentrate, 49% in the zinc concentrate and 23% in the final tailings, whereas at other deposits Ag is typically a co-product of Cu or Pb sulphide flotation. The consistently poor Ag recovery and unusual distribution was thoroughly investigated, a mineralogical plan being devised to determine whether these results were related to the nature and mode of occurrence of Ag carriers. Work was performed to determine discrete Ag-bearing minerals and/or Ag contained in solid solution in a suite of commonly occurring sulphides, by means of ore microscopy, SEM methods, electron microprobe and ion microprobe analyses. It was concluded that Ag at Lady Loretta is strongly associated with sphalerite and that options available for increasing its recovery are limited to improving Zn recoveries and negotiating appropriate sales contracts with Zn refineries.
The Queensland deposit averages 5.9% Pb, 17.1% Zn and 97 g/t Ag, mostly in fairly complex intergrowths of pyrite, sphalerite and galena. Average silver distribution from four pilot plants was 28% in the lead concentrate, 49% in the zinc concentrate and 23% in the final tailings, whereas at other deposits Ag is typically a co-product of Cu or Pb sulphide flotation. The consistently poor Ag recovery and unusual distribution was thoroughly investigated, a mineralogical plan being devised to determine whether these results were related to the nature and mode of occurrence of Ag carriers. Work was performed to determine discrete Ag-bearing minerals and/or Ag contained in solid solution in a suite of commonly occurring sulphides, by means of ore microscopy, SEM methods, electron microprobe and ion microprobe analyses. It was concluded that Ag at Lady Loretta is strongly associated with sphalerite and that options available for increasing its recovery are limited to improving Zn recoveries and negotiating appropriate sales contracts with Zn refineries.