Biosolids (peat and FYM) and mineral solids (clay and zeolite) were compared for their effects on the mobility of six heavy metals: Cr, Ni, Pb, Cu. Zn and Ni under progressive acidification in a Hungarian mine spoil. Successive decline in pH enhanced the mobility of the heavy metals due to dissolution. Solubility behaviors of heavy metals followed the order Cd = Zn > Pb = Cu > Ni = Cr showing that metal ion pairs Zn – Cd, Pb – Cu and Ni – Cr had almost similar mobilities ranging between 29.34 – 34.54, 61.89 – 63.35 and 68.94 – 70.73 %, respectively under extremely acidic environment. Biosolids enhanced the mobility (by 1.16 – 11.69 %) in the order: FYM > peat over control owing to the dissolution of stable metal complexes; whereas mineral solids reduced it (by 3.39 – 14.05%) following the order: zeolite > clay due to retention of metals. The results suggested that polluted mine spoils should be amended with mineral solids like zeolite to reduce the risk of heavy metal contamination.