The potential of thermophilic sulfide-oxidizing archaea in copper extraction has attracted interest due to the efficient extraction of metals from sulfide ores that are recalcitrant to dissolution. Microbial leaching is especially useful for copper ores because copper sulfate, as formed during the oxidation of copper sulfide ores, is very water-soluble. Approximately 25% of all copper mined worldwide is now obtained from leaching processes. The acidophilic archaea "Sulfolobus metallicus" and "Metallosphaera sedula" tolerate up to 4% of copper and have been exploited for mineral biomining. Between 40 and 60% copper extraction was achieved in primary reactors and more than 90% extraction in secondary reactors with overall residence times of about 6 days.