The bioleaching effects of two microorganisms on two different enargite (Cu3AsS4) minerals have been followed by solution titration and rest potential measurements and studied by cyclic voltammetry. The investigation focused on the superficial modifications produced in the minerals by the activity of the mesophilic bacterium Acidithiobacillus ferrooxidans at 35 °C and the thermophilic archaeon Sulfolobus sp. at 68 °C after 3 and 12 days of attack, comparing the modified surfaces with that of untreated samples. The electrochemical characterization of all the electrodes was done by means of potentiometric assays performed under the same conditions: acidulated deionized water as electrolyte (pH 2.0), and temperature of 26 ± 2 °C. Additionally, a comparative SEM and EDX study of untreated and biotreated samples was carried out.