Acidic ferric ion, an effective and important oxidizing agent for mineral leaching, is usually produced by direct dissolution of the corresponding salts into the solution or can be prepared in‐situ or in separate aerated batch reactors by chemical oxidation of iron sulfide through a number of different processes. The purpose of this paper is to present the idea and the results of generating the useful ferric leaching medium by bacterial oxidation of pyrite under the commercial leaching conditions in an underground copper mine. The information presented deals mainly with factors promoting the continuous oxidation of pyrite by iron‐oxidizing bacteria and the related factors influencing the extraction of copper from the enargite. This is the first attempt to produce a ferric leaching medium in an underground mine by a microbiological process. The generation technology and engineering layout are also discussed.