Summary The distribution and diversity of acidophilic bacteria of a tailings impoundment at the La Andina copper mine, Chile, was examined. The tailings have low sulfide (1.7% pyrite equivalent) and carbonate (1.4% calcite equivalent) contents and are stratified into three distinct zones: a surface (0‐70‐80 cm) ‘oxidation zone’ characterized by low‐pH (2.5–4), a ‘neutralization zone’ (70–80 to 300–400 cm) and an unaltered ‘pri...