Borax in Gold Mining?

          On Thursday, after my presentation on Gold Mining and Pollution in the Pantanal, someone asked whether all gold miners use Mercury in their mining operations. While industrial mining companies use other toxic chemicals to extract gold from quartz fragments, there is, in fact, a non-toxic option that artisanal miners can use: borax. Gold-mining with borax already occurs across thousands of mines in the Philippines, so it could easily make its way to South America. 

               Borax (Sodium Borate) is an inexpensive chemical commonly used in household cleaning products like detergents. Because it is inexpensive, it makes a good alternative to mercury in the gold mining process because impoverished small-scale miners have access to it.

               While mercury causes Gold flakes to conglomerate into pellets, borax functions by lowering the melting point of gold. Gold’s normal boiling point is over 1000 degrees, which is much higher than what a small-scale miner could feasibly reach with a cheap burner. However, Gold melts much more readily in the presence of borax, making it possible for miners to heat their centrifuged concentrate to produce molten gold. The process occurs in five steps: grinding, washing, mixing, heating and extraction. Gold ore is first crushed, then “washed” in the stereotypical gold pan, mixed with borax in a 1-to-3 ratio by volume, heated over a coal or acetylene fire, and removed once gold drops have accumulated.

The shining gold pellet and molten red borax that result from this process

This process makes no use of mercury, which makes it much safer for both the miners and the environment surrounding the mining operation. Borax is “environmentally benign,” so accidental releases of it during the mining process are a nonissue.

Source: http://www.geus.dk/program-areas/common/the_borax_method_2011.pdf