According to the GEUS, the Geological Survey Office of Denmark and Greenland, it is possible to concentrate and isolate gold from the ore using borax and charcoal. This method has the immediate benefit of making mercury “redundant” in gold isolation.
Extraction of gold by amalgamation with mercury is a simple means of producing metallic gold in the field. After contact with gold enriched ore, mercury is evaporated into the air by direct application of a torch flame to the puddle of metal leaving purified gold metal.
It is thought that there are millions of miners who scratch out a subsistance living working a small patch of ground for gold. It’s called small scale mining. In the course of this activity, environmental contamination can accrue to the immediate area as well as the watershed at large. Sadly, the toxicological insult to the miners from exposure to mercury vapor can be severe.
This method is an inexpensive and simple alternative to the mercury process. Perhaps the chemistry community has something to contribute by way of education or improved methods of extraction.
8/25/10 Update. I have revisited this post and am compelled to comment further. While I am unable to offer a good chemical explanation for the effect of borax on gold ore, I can say that the use of borax as a flux for smelting goes back to the 19th century during the American gold rush period. The process described in the link appears to be a smelting process for enriched ore containing elemental gold, as opposed to sulfide, or sulphuretted ore. The function of a flux is to modify the flow and phase separation properties of host rock so as to partition away from the gold phase or layer. In other words, a flux modifieds the slag to help the gold to separate cleanly from the rock.