Cumulative assays of head and tail do not always equal recovered gold. This may be due to mineralogical factors, such as the presence of refractory gold, grain size and shape, host associations, liberation, or due to issues with the metallurgical process. Modern microscopy techniques can afford exacting quantification of gold presence as well as a description of its environment and 3D morphology. The dispersion of non-liberated, sub-micron (down to a few nanometers) gold phases within a host or hosts can now be measured, as can the effects of grain morphology on recoverability in a circuit.
In this paper we will present advances in scanning electron microscope (SEM)-based automated quantitative mineralogy (AQM) analysis of gold ores that quantifiably and consistently account for the presence of nanometer-sized gold grains. We will also elaborate on the application of 3D X-ray microscope (XRM) techniques that offer several advantages over 2D techniques when analyzing the cause of gold losses to tailings. The use of XRM removes the need to analyze a multitude of samples in 2D to adequately interpret a 3D environment, and reduces the number of samples needed for the detection of phases present in trace proportions (i.e., low grade gold).