In this paper unleached gold refers to residual solid gold in the leach tails that did not leach during processing in a CIP/CIL circuit but can be leached subsequently in the laboratory. A benchmarking survey conducted during the Amira P420G project in 2021 showed that the average gold grade of the leach tails solids from 22 sites was 0.21 g/t. At a gold price of US$4000 per ounce, the average value of the gold contained in the leach tailings solids is US$27/t. If the leach tails solids grade drops by 0.02 g/t through increased gold recovery, an additional US$2.6 M per million tonnes (Mt) of ore processed can be realised. Understanding the causes for unleached gold is essential for leach circuit optimisation and maximising revenue. This paper presents the factors affecting gold leaching and the challenges associated with assessing the nature of the unleached gold in leach tailings. A case study is presented to illustrate the methodology to determine the nature of the unleached gold in leach tailings as well as potential options to improve gold recovery. Modelling shows a significant portion of the gold present in the leach tailings solids can be leached when subject to additional leaching time in the presence of sufficient cyanide and oxygen.