Eliminating mercury-use in artisanal gold mining

Materials World magazine
29 Jan 2020

A new process could help artisanal miners leach gold without using mercury, but can it work? Idha Valeur reports.

A new separation process that isolates gold without the use of mercury was tested during January 2020, in a bid to present artisanal gold miners with a safer, low-cost extraction method. The system, called GOLDROP, was tested under the leadership of the non-profit organisation (NGO), Mercury Free Mining (MFM).

MFM’s goal is to make gold extraction safe and increase the efficiencies currently possible with mercury. The NGO believes that if the benefits of the new technology are instant and obvious, they can onboard miners to using the technique quite quickly.

Mercury is a common and acceptable means of extracting gold from ore, and is a staple practice in both large and small operations. However, problems arise from incorrect handling or when there is no personal protection gear or infrastructure preventing it from leaching into the groundwater, which risks polluting water sources and damaging communities, crops and lifestock. As artisanal and small-scale miners (ASM) are less likely to have access to these resources, the project is aimed at helping them get results without using mercury.

The GOLDROP system

GOLDROP was invented by Sluice Goose Industries Founder, John Richmond. His system uses gravimetrics to separate gold from paydirt following crushing and milling to bring it down to a fine particle size.

The all-in-one kit consists of 19 parts and weighs approximately 20.4kg, and according to the company, it is designed to be easily moved around, sturdy and simple to use. Only water is required to make the system work. First, the material is added to the feeding funnel which is located at the top of the separation system. The water flow enables the gold to be separated from the dirt almost instantly, while dirt can be added to the funnel in a continuous stream.

‘As the GOLDROP separates the gold, the tailings are fed out through the back of the unit into an optional bucket or back onto the ground,’ the company said. The gold ends up in a jar, which is located at the end of the system.

The testing

On 8 January, jeweller, designer and MFM CEO, Toby Pomeroy, travelled to Ghana with the GOLDROP separation system to start a period of testing, in collaboration with the University of Mines and Technology in Tarkwa, Ghana.

‘Miners in three artisanal mining communities in the Ashanti region will use the GOLDROP equipment in daily, real-world applications. The results will be scientifically monitored, documented, and reported,’ Pomeroy said.

After the first day of testing, Pomeroy reported that Ghana National Artisanal and Small-Scale Miners Association (GNASSM) National Organiser, Anaji Baba, had observed the testing and had recorded that the team was capturing 95% of the alluvial gold the miners were processing.

‘These miners pick up the GOLDROP almost immediately. We are learning a lot about the tool’s capabilities as well as possible improvements upon return,’ Pomeroy stated in a MFM blog. However, on 14 January, Pomeroy said the team testing day in Tarkwa hard rock mine had yielded mixed results.

In a Facebook post, Sluice Goose shared reports that the Ghana project was proved successful, and that the ASM miners had offered insights on improvements that could be made to further develop the system. Going forward, MFM is seeking investment to develop and refine the GOLDROP method.