The mineral dundasite was first described by W. F. Petterd in 1893, a ‘Catalogue of Minerals known to occur in Tasmania’. It was found in small, silky, milk-white, spherical aggregates incrusting a ‘ferro-manganese gossan’ at the Adelaide Proprietary mine, Dundas. In this catalogue, and in a subsequent one dated 1896, it was stated, as the result of qualitative tests, to be a hydrated carbono-phosphate of lead and aluminium ; but a quantitative analysis (see below under II), made later by S. Pascoe, showed that the mineral is a hydrated carbonate of lead and aluminium, and that the traces of phosphoric acid were due to a thin coating of pyromorphite. In this analysis the water and carbonic acid were determined together, by loss on ignition, and consequently hitherto no chemical formula has been attributed to the mineral.