Effect of pyrrhotite on gold leaching

Abstract

The recovery of gold from its ores by cyanide leaching has been practiced around the world for more than a century. One of the parameters that dictate the rate of gold leaching as well as the rate of reagent consumption (lime and cyanide) is the mineralogy of the ore being processed. The influence of the inherent composition of the ore as well as the addition of minerals is known to affect the operation of the leaching operation. There are several conflicting views with respect to the influence of pyrrhotite on gold leaching reported in the literature and these are summarised. Some details of how the presence of pyrrhotite influences the solution chemistry of the leach solution are also presented. The effect of the presence of pyrrhotite was investigated by reporting the gold leaching data from a number of characterised systems. Although pyrrhotite is often considered deleterious to cyanidation, provided the level of dissolved oxygen is maintained at a reasonable level, gold leaching rate remained unaffected.