Orpiment, getchellite and stibnite from Zarshuran deposit, NW Iran, exhibit extensive As-Sb substitution. There are four known minerals along As2S3-Sb2S3 join, i.e. orpiment (As2S3), Wakabayashilite [(As,Sb)20S30], getchellite (AsSbS3) and stibnite (Sb2S3). Extensive mineralogical studies by scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA) indicate that getchellite fr...