Recovering Gold With an Arrastra and Mercury - Third World Artisanal Mining

In this video they reprocess 10 sacks of ore to recover the final bit of gold using mercury. The process is very time consuming and inefficient - it took about 8 hours to complete. In this setting mercury only recovers about 35% of the gold and almost none of the free silver. They add lime and powdered soap to cut down on oils in an effort to increase the recovery. They also add lime juice to the mercury to "clean it" prior to its use. The lime provides a small quantity of citric acid to the process.