Enhancing Environmental Quality through Improved Gold Recovery in Artisanal and Small-Scale Gold Mines in Tanzania.

The project was financed by the Belgian Technical Corporation and carried out by Peter Appel and John Tychsen, Geological Survey of Denmark and Greenland

Mining operations, gold extraction processes and environmental problems have been investigated in three small-scale mining communities. Itumbi near Chunya is a community where small-scale mining has been the main source of income for decades. Londoni near Manyoni used to be a small sleepy village with a few hundred inhabitants. A few years ago gold was found and a major gold rush with more than 10.000 small-scale miners rushing to the village. Mpambaa near Singida is an area of farmland where gold was found February 2009. This resulted in a small gold rush.

Samples of every step in gold extraction have been collected. Samples of tailing have also been collected. The samples have been analysed for gold and some of them for mercury as well. The assay results show that the techniques used by small-scale miners in not very efficient. The miners loose a lot of gold and release lots of mercury to the environment.

The results of the present project indicate that the first steps in increasing recovery of gold for the small-scale miners seems to be better milling techniques and improved sluices. The best available technique (BAT) for gold extraction in both communities is borax. This technique is able to extract as much gold as the presently used mercury technique, but without negative environmental and health impacts.

The non toxic borax gold extraction technique was tested on a number of samples of gold concentrates from the three communities. All samples proved to be amenable for using borax in gold extraction. If this method is adopted by the small-scale miners then use of mercury will stop. Alternatively mercury recycling can be introduced. This will reduce release of mercury to the environment with more than 90 percent.

Soil sampling in maize fields in and around Itumbi and Londoni showed high concentrations of mercury. Disturbing was the discovery of a soil sample collected more than 10 km from any small-scale mining site which carried high amounts of mercury. This indicates that the mercury pollution from gold extraction is distributed over vast distances. These results show that mercury from small-scale gold mining causes regional health hazards for the population of Tanzania.

Burning amalgam

The finding from the project was presented to a group of stakeholders at a workshop on 21st of October 2009. NEMC and the Consultant received a number of very valuable comments and recommendations, which can be summarize to the following:

  • A genuine need of improving gold recovery and reduce mercury pollution of the environment.
  • Representative of small scale miners agree that there is importance of introducing Borax method in recovering gold.
  • NEMC should organize a workshop where by small scale miners from pilot areas (Itumbi and Londoni) will explain to their fellow colleagues how efficiently borax works in recovering gold. The alternative of the use of gas instead of charcoal should be considered.
  • NEMC will work with stakeholders in taping in the existing funds from Minerals Development fund (under Ministry of Energy and Minerals) and others to ensure that small scale miners and artisans use best available technology such as borax.
  • A cost benefit analysis should be conducted comparing the use mercury versus borax.
  • Improvement of the existing processing mechanisms such as efficient use of clothes and retort for recycling of gold.
  • Introduce the use of borax in selected pilot areas. The small-scale miners present at the workshop found the suggestion of bringing in a small-scale miner from the Philippines to Tanzania in order to teach them using borax as excellent. This will be done during the last two weeks of January 2010.

Project carried out under the auspices of Geological Survey of Denmark and Greenland (GEUS).

The final report can be downloaded here Tanzania2009report (pdf 3.1MB)