Optimum pH, temperature and pulp density for microbiological leaching of museum-grade stibnite mineral has been investigated using a stibnite-adapted strain of Thiobacillus ferrooxidans. Optimum conditions were found to be pH 1.75, 35 C and 12g solid substrate per 100 ml of basal salts medium as the initial dose. The energy of activation was determined to be 16.8 kcal per mole, and the temperature coefficient 2.2. The highest total dissolved antimony concentration, [Sbt] = [Sb+3] + [sb+5] + I1SbO2+], was about 1400 mg/litre, due to relatively low solubility of (SbO)2SO4 and (SbO2)2SO4.