Bacterial and chemical oxidation of gold-bearing pyrite gives rise to not only ferric sulfate and sulfuric acid but also ferrous sulphate and low-valence oxide of sulfur. The potential in the system is too low to dissolve native gold to form Au(SO4)2- Experiments indicate that gold does not dissolve in sulfatic iron solution. When oxidation becomes stronger and the pH value of the media is greater than 4 so that the thiosulfate root may exist stably, gold may dissolve as stable thiosulfate complexes.