Tracking ore mineral characteristics from mine to concentrate: The fate of electrum at the Cavanacaw gold deposit, Northern Ireland

A systematic geometallurgical assessment was carried out to follow changes of mineral composition and microfabric following the ore extracted from two ore blocks at the Cavanacaw Au Mine through the beneficiation process. SEM-based image analysis was used to carry out the investigation on the finely disseminated Au ores. A general assessment quickly reveals that the beneficiation plant suffers only little loss to the tailings. Despite this positive assesment results illustrate that there are some losses that appear to be systemic: Large electrum grains (>16 µm ecd) are abundant in the original uncrushed material only make a minor contribution to the final concentrate. Due to the ductile behaviour of electrum, fracturing of larger electrum grains into smaller grain sizes appears unlikely – it is thus concluded that these particles may be captured in the plant during processing.
Our results reveal that sulphide-rich veins are typically higher in grade than the final concentrate. This results from processing a mixture of high-grade ore and low-grade wall rock. To reduce processing costs it might be considered to introduce an early stage of optical sorting