Characterization and Gold Assaying Methods in the Assessment of Low Grade Gold Ore from Malaysia

Abstract

The low grade gold ore obtained from a local gold mine in Malaysia was characterized using X-ray fluorescence analysis and scanning electron microscope/ energy dispersive X-ray analysis for the deportment of gold. Acid digestion was carried out to determine iron, aluminium, sulphur and arsenic using ICP-OES. Chemical assaying methods viz aqua regia leaching and lead fire assay followed by acid digestion were conducted to determine the head grade of the gold ore. Assessment of gold using fire assay was found reliable to reduce the interferences from the gangue minerals. Despite the lower limit of detection of ICP-OES, there was no appreciable amount of gold detected in the samples leached using aqua regia because of the interference from the gangue minerals and also due to the interlocking of gold with aluminosilicates phase which require high pressure and temperature leaching using hydrofluoric acid to liberate the gold. ICP-OES analysis is reliable depending on the degree of liberation of gold during acid digestion. The head grade for this type of low grade gold ore was found to be in the range of 0.31 g/t to 0.55 g/t where the gold was highly associated with aluminosilicate minerals.