Disordered intergrowths in lead-arsenic sulfide minerals and the paragenesis of the sartorite-group minerals

High-resolution transmission electron microscopy has been used to investigate disordered structural intergrowths in lead-arsenic sulfide minerals that occur at Lengenbach, Binntal, Switzerland. Most of the material examined was found to be perfectly ordered; however, some highly disordered specimens were found. The "disordered liveingite', compositionally intermediate between dufrenoysite and liveingite, was found to be a disordered intergrowth of sartorite-like units and dufrenoysite-like units. This disordered intergrowth represents a transitional stage in the replacement of dufrenoysite by the more As-rich mineral liveingite. -from Author