Refining gold ores using mercury is one of the easiest and cheapest way.
But, as written on this sign, mercury is highly toxic. Thus, in western countries, it is forbidden to use it in the process. Unfortunately, Peruvian gold miners have little other options, and are exposed to its effects more than ten hours a day.

Date: Wednesday, November 30 2005
Camera: NIKON D70
Focal length: 55 mm
Aperture: f/6.3
Exposure Time: 1/160 sec
Flash: Not Fired