At the Herbert East prospect on the Herbert Glacier pyrite, pyrrhotite, minor chalcopyrite and sphalerite occur in an Upper Triassic, light green-weathering, andesitic volcaniclastic unit which is about 15 metres thick. The unit is traceable for 150 metres, pinches out to the south and is downfaulted under the Herbert Glacier to the north. The mineralized andesite is overlain by a continuous bed of siliceous massive pyrite and pyrrhotite 47 centimetres thick and assaying 8.58 grams per tonne silver, 0.14 grams per tonne gold, 0.051 per cent copper, 0.024 per cent lead, 0.330 per cent zinc, and 0.017 per cent cobalt (Assessment Report 12629). This is in turn overlain by about 15 metres of black, carbonaceous shale, with over- lying pillow basalts.