Jarosite

Abstract

Jarosite is a family of iron-hydroxysulphate minerals that commonly occur in acidic, sulfate-rich environments, and mining and ore processing wastes. End-member jarosite sensu stricto contains potassium and has the chemical formula KFe3(SO4)2(OH)6, but extensive element substitution takes place in the crystal structure for potassium, iron, and sulfur. Other jarosite group minerals include ammoniojarosite, argentojarosite, natrojarosite, and plumbojarosite, in which ammonium, silver, sodium, and lead, respectively, substitute for potassium. Environments in which jarosite group minerals commonly form as secondary minerals include the oxidized zones (gossans) of sulfide ore deposits, areas of acid mine drainage, and acidic soils. In supergene enrichment zones of sulfide-bearing ore deposits, silver-bearing jarosite deposits can be an economically important mineral source of silver. In environments such as mine wastes, jarosite minerals are able to scavenge and act as sinks for potentially toxic elements such as arsenic and lead. Jarosite minerals are potential sources of acid generation in stream systems, breaking down to release sulfate and hydrogen ions, as well as metal cations including iron, potassium, trace metals and other contaminants, when they are removed from their stability region. Jarosite precipitation is used in hydrometallurgy, especially the zinc industry, to control iron, sulfate and other impurities.