Refractory gold ores and concentrates part 2: gold mineralisation and deportment in flotation concentrates and bio-oxidised products

Gold mineralisation and deportment in two refractory flotation concentrates and their corresponding bio-oxidised products were investigated using several analytical techniques. One concentrate and its product show higher gold grades (28 and 38 g/t, respectively) than the other (17 and 23 g/t, respectively). The results showed that both visible, polydispersed and invisible gold particles were present in all four samples. The invisible gold was disseminated in arsenian pyrite and arsenopyrite mineral phases. Unliberated, visible gold particles were in complex gold associations with sulphides, silicates, and oxides. In addition, visible gold-sulphate mineral associations were also noticeable in the bio-oxidised products. Marked differences in gold mineralisation and association such as occurrence of gold in muscovite and jarosite-cemented gangue mineral agglomerates were notable between the two bio-oxidised products. Furthermore, combined jarosite and gypsum mineral encapsulation accounted for approximate to 43 wt.% Gold refractoriness in the lower gold-bearing bio-oxidised product.