What are sulfosalts in mineralogy ?
Sulfosalts : definition
The sulfosalts subclass (about 155 minerals) is complex. It differs from that of sulfides in that As, Sb or more rarely Bi play the role of metallic element (reducing cations) in the crystalline structure. As and Sb are then in the form As5+ and Sb5+. The case is very different from that of sulfoarsenides such as arsenopyrite (FeAsS) for example, in which As subsitutes S, thus playing the role of anion.
They are generally quite accessory minerals of Cu, Ag or Pb (boulangerite, bournonite, semseyite, jordanite...). Only a small number of them sometimes constitute ores (enargite, Cu3AsS4 copper ore ; pyrargyrite, Ag3SbS3 silver ore...).
The term sulfosalts, however, has different meanings depending on the authors. The distinction between sulfides and sulfosalts is not always possible on simple examination of the chemical formula, and only a study of the crystal lattice then makes it possible to decide.
They are generally quite accessory minerals of Cu, Ag or Pb (boulangerite, bournonite, semseyite, jordanite...). Only a small number of them sometimes constitute ores (enargite, Cu3AsS4 copper ore ; pyrargyrite, Ag3SbS3 silver ore...).
The term sulfosalts, however, has different meanings depending on the authors. The distinction between sulfides and sulfosalts is not always possible on simple examination of the chemical formula, and only a study of the crystal lattice then makes it possible to decide.
Boulangerite from St-Pons, Alpes de Haute Provence
Bournonite from Les Malines, Gard, France
Semseyite from Peyrebrune, Tarn, France - © Guy Bernadi