Sunday, April 30, 2017

Mercury Use in the Guinean ASGM Sector


The ASGM sector in Guinea is vibrant, growing, and ripe with opportunity. If properly managed, it could create a much needed West African example of best practices in ASGM.

The Artisanal Gold Council (AGC) is engaged in a United Stated Department of State (USDoS) funded project focused on reducing mercury use in Francophone West Africa. The project currently is active in Senegal, Burkina Faso, and Guinea. Here we will discuss the interesting and unique approach to mercury use in Guinea, which differs from common practices seen in surrounding West African countries.

Traditional gold concentration process using a calabash pan

While traditional gold mining has occurred for centuries in Guinea, there has been significant growth in modern ASGM in recent years, including the introduction of mercury to amalgamate gold. 

The Guinean ASGM sector is less developed (delayed) compared with the longer standing activities of surrounding countries (for example in Mali), and this is reflected in a simplified, less mechanized ASGM sector, and interestingly, less mercury intensive practices in Guinea. The young status of the country’s ASGM sector provides opportunities to prevent bad practices that have become more strongly entrenched in more developed ASGM sectors. 


In nearby countries (Senegal, Mali, Burkina Faso) mercury use is pervasive and present in almost all ASGM processing operations. The common West African process is to remove ore from the mines, crush, mill, concentrate using sluices, and amalgamate the sluice concentrate on site with mercury. The amalgamation and burning of amalgam is usually conducted on site by the processors or site bosses. This spreads mercury use widely to various ASGM sites, making controlling and reducing use difficult. Guinea differs. 

In Guinea, the initial process is similar (although commonly using less mechanised crushing and milling practices), but the resulting concentrate is further upgraded using pans and magnets (to remove magnetic minerals) to produce a very high grade, almost pure, gold dust. This high grade concentrate is brought to gold buyers in local mining hubs, where the buyers themselves provide mercury to the miners to amalgamate the concentrate on the buying site. In effect, this approach restricts mercury use to only the buying sites, rather than spreading further upstream in the production system to throughout the rural mining regions.

This difference in amalgamation approach provides easier opportunities to reduce and ultimately eliminate mercury use than in surrounding countries. The time for intervention is now, before mercury spreads upstream to the processing sites. Training and interventions provided now can ensure this does not occur. Interventions for mercury reduction with the gold buyers where the majority of mercury use occurs are also possible. Reduction options include:
  • Training of gold buyers in direct smelting, to allow the smelting of high grade gold dust directly, rather than the amalgamation with mercury. This may not be feasible for all purchases as larger volumes of material are needed for direct smelting, and individual miners or small miner groups often bring small amounts of gold dust for sale at a time;
  • Implementation of retort or fume hood programs on gold buying sites to further reduce mercury loss and human exposure during amalgamation and burning – see needed precautions in AGC’s retort guide on this page of our website;
  • Early onset technical interventions on mine sites to demonstrate improved gravimetric processing workflows, and direct smelting, which will allow miners and processors to produce gold ingots themselves on site, before they are introduced to the often easier (although lower recovery) mercury intensive processes commonly practiced on site in other West African countries.

Celebration for the national day of the artisanal miner in Kankan, showing president Alpha Condé giving a speech (above) and the attending crowd (below)





The Guinean ASGM sector is large and unique. Miners are friendly and keen to learn and adopt improved practices to reduce potential negative health and environmental impacts associated with artisanal mining. Additionally, the Government of Guinea has made improving the governance and reducing the negative environmental impacts of ASGM a priority. This commitment is evidenced by an ongoing reform of existing policy and legislation pertaining to ASGM, culminating in the official opening of the country’s first four dedicated ASGM mining corridors in Siguiri on February 6, 2017 – suitably on the national day of the artisanal miner. Remarkably, this is a celebration of artisanal mining in Guinea. Something many other countries might consider doing in order to raise awareness of the positive aspects of artisanal and small scale gold mining. It was held in Kankan, and attended by over 1000 stakeholders, including government, business, NGOs, and countless miners and community members interested in learning how changes could improve or worsen their ASGM based livelihoods.






2 comments:

  1. Mine is question. How much mercury does it take to recover over time a 100kg of gold? I'm just trying to put things in perspective for some ASGM who dont realise that they produce lots of gold.....in the process pollute a lot!

    ReplyDelete
  2. Hi Jules. The quantity of mercury required to recover 100 Kg of gold varies depending on several factors such as the practices adopted on site (i.e amalgamation of concentrate vs. whole ore) but on average the quantity used is typically 1.5 times greater than the amount of gold recovered (~150 Kg of mercury used in this case). Other relevant factors include the quantity of silver present in the ore as it can significantly increase the amount of mercury needed for amalgamation (i.e. up to 4 times higher), and whether or not any mercury is being captured and recycled/reused (i.e. retort use, etc.) which would decrease emissions and the amount required over time.

    ReplyDelete

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