Abstract: Pyrosmalite [(Mn,Fe)₈(OH,Cl)₁₀Si₆O₁₅] has been identified by X-ray diffraction from the Pegmont lead-zinc deposit, north-west Queensland. Microprobe analyses indicate that it is the first reported occurrence of an extremely iron-rich member of the series. The characteristically high chlorine content of pyrosmalite in Pegmont and other similar base metal deposits may provide some evidence concerning the depositional environment of these stratiform Pb-Zn ores.