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.
Southeast Missouri Lead District sphalerite, and chalcopyrite. Gangue minerals associated with the economic minerals include pyrite, calcite, dolomite, and quartz. Specimens from the Lead Belt are highly prized by gem and mineral collectors and are found in museums worldwide. The ore minerals of the Lead Belt are primarily hosted by bacterial stromatolite reefs and associated oolitic rocks of the dolomitic Bonneterre Formation. This Cambrian age formation was deposited in a shallow sea around the Precambrian age St. Francois Mountains, which formed an island archipelago. Ore mineralization most likely occurred during the late Pennsylvanian and/or Permian periods when warm metal and petroleum bearing fluids from