Comparison of Gold Yield with Traditional Amalgamation and Direct Smelting in Artisanal Small-Scale Gold Mining in Uganda

Background. The amalgamation method used by artisanal small-scale miners is the single largest source of global mercury emission. The goal of the ‘Free Your Mine’ project is to stop mercury use in artisanal and small-scale mining. Objectives. The aim of the present study was to compare gold recovery and time consumption between the amalgamation method and direct smelting, using borax for smelting under standardized conditions. Materials and Methods. This was an experimental study in a pragmatic setting in the mining community of Tiira, Uganda. Standardized amounts of gold ore of equal quality were processed with the local amalgamation method and with the Philippine mercury-free method as practiced by miners from Benguet in the Philippines, and the gold yield and time consumption were compared. Results. The amalgamation method took 53 minutes and recovered 1.0 g of pure gold. The miners used 4 g of mercury in the processing. The Philippine mercury-free method took 62 minutes and recovered 1.4 g of pure gold. Conclusions. The Philippine mercury-free method recovered 40% more gold than the amalgamation method but took 9 minutes longer. The Philippine mercury-free method is a viable alternative to amalgamation. Competing Interests. The authors declare no competing financial interests.