Native Lead at Broken Hill, New South Wales, Australia

Native lead, a rare mineral, occurs in a late-stage vein in the world’s largest lead – zinc – silver deposit, at Broken Hill, Australia. The lead-bearing vein consists mainly of laumontite, quartz, biotite and muscovite, together with minor amounts of lead, galena, sphalerite, molybdenite, and rare allanite-(Ce). Three types of fluid inclusions have been identified: two-phase brine inclusions lacking daughter crystals, brine inclusions “packed” with daughter crystals, and vapor-only inclusions. These fluid inclusions, together with stability data for coexisting minerals, indicate that the native lead formed by precipitation from lowtemperature (270–300°C) brines in a near-surface, low-pressure environment. The 207Pb/204Pb value for the native lead differs significantly from the values for galena and amazonitic orthoclase from the Broken Hill orebody, but overlap the array defined by galena in Cambrian epithermal deposits in the region.