Acid mine drainage where the ore is a sulfide mineral or is associated with pyrite. In these cases the predominant metal ion may not be iron but rather zinc, copper, or nickel. The most commonly mined ore of copper, chalcopyrite, is itself a copper-iron-sulfide and occurs with a range of other sulfides. Thus, copper mines are often major culprits of acid mine drainage. At some mines, acidic drainage is detected within 2–5 years after mining begins, whereas at other mines, it is not detected for several decades. In addition, acidic drainage may be generated for decades or centuries after it is first detected.
Broken Hill ore deposit mining is concentrated in the Blackwood Open Cut, which commenced in 1973, and the Kintore Open Cut. Stope fill, plus remnant supergene silver and sulphide ore characterize the ore reserve. Pasminco Limited took over the leases of The Zinc Corporation, Limited, and New Broken Hill Consolidated Limited. Their main shafts included ZC, NBHC and Southern Cross. These ZC Mines Leases lie south of the MMM Mining Leases along the Broken Hill "line of lode". By the early 1950s the Broken Hill area had suffered a major drought of over 8 years which was close to shutting down the mining operation.