• Critical conditions for galena transformation to lead jarosite are 130°C, 30 g/L H2SO4, 15 g/L Fe3+, and 0.4 MPa O2 partial pressure.
• Higher Fe3+ and O2 pressure do not enhance jarosite formation; lower temperature and higher acidity favor PbSO4 and inhibit jarosite.
• Potassium, sodium, and high zinc sulfate all inhibit jarosite formation; potassium sulfate promotes potassium jarosite instead.
• High zinc sulfate alters product morphology and coprecipitates with lead jarosite, affecting residue composition.