Mineralogy and texture of a wet table gravity gold concentrate from Coronation Hill, NT, with notes on the occurrence of platinum and florencite.

Abstract

The report is an internal BHP Exploration Department memo reporting results of a mineragraphic study of a single specimen of surface gold mineralisation from Coronation Hill. Gravity concentrates were examined and selected grains subjected to scanning electron microscopy and microprobe investigation. The study revealed the presence of gold, silver-bearing gold, stibiopalladinite (Pd3Sb), native palladium, and rare native platinum. Gold forms intergrowths with stibiopalladinite and native palladium, the latter often forming rims around stibiopalladinite in contact with gold. Platinum occurs as minute grains (<1micron) as inclusions in native palladium. A rare earth mineral, florencite [(Ce,La,Ca) Al3 (PO4)2 (OH)6] is found in places closely associated with the precious metal grains. A provisional ore dressing route is suggested. It is noted that the amount of Pt observed is insufficient to explain the Pt assays recorded. Selenides are absent from the specimen, presumably because the specimen is from surface.