INNOVATION January-February 2017

f ea t u r e s Gold and Mercury; Payment and Poison Despite being inefficient and unsafe, mercury is a key component of artisanal gold mining and extraction in many developing countries. After working for weeks in his or her mine, river or shaft, an artisanal miner takes the ore that has been collected to a processing centre. Using basic machinery, such as small ball mills, gold is extracted by adding mercury to bond with free gold in the crushed ore. This process recovers about 20 percent of the gold. The miner receives a lump of the resulting amalgam, an alloy of roughly equal parts gold and mercury. The centre then reprocesses the ore using a more efficient process, such as cyanidation, to extract up to 90 percent of the remaining gold. Carrying the amalgam in his or her hand—pleased to have been ‘paid’ with something tangible after weeks of labour— the miner walks to a gold shop or to their home. There, they use a blowtorch or similar tool to burn the amalgam and recover the gold. That gold can be used immediately to buy food, pay off debts, or buy property. The process also releases toxic mercury gas into the air. Mercury: A Global Problem Breathing airborne mercury can damage the nervous, digestive and immune systems. It can harm lungs and kidneys. It can cause brain damage in unborn children. It can even kill. Airborne mercury settles on clothing, surfaces, in soils and sediments of waterways, and, says Veiga, tailings treated with mercury and then cyanidation form soluble mercury cyanide that

leaks into waterways and accumulates in fish species. A 2013 UN Environment Programme report lists the artisanal and small-scale gold-mining sector as the largest contributor (37 percent) of global mercury emissions to the atmosphere. Many of the countries that emit the highest amounts of mercury also have the most artisanal gold-mining activity. Mercury vapour in the air around processing centres and other amalgam-burning sites is much higher than limits set by the World Health Organisation. It is a growing global problem that is deepening as economic crises drive more people to artisanal mining. “Artisanal mining is the main environmental and social problem we have in mining today,” Veiga says. “It’s important for governments and companies to understand the problem here is not environmental. The environment is a consequence of this. It is a social problem, driven by poverty and lack of economic alternatives.” Eliminating mercury from artisanal mining and extraction must be the priority, Veiga says. However, although efforts to restrict the use, sale, and spread of mercury contamination are underway, progress is slow. Most artisanal miners are unaware of the dangers and damage they cause. The artisanal-mining sector is largely invisible. Furthermore, the size of the problem is both under- estimated and relatively unknown. For example, Canada is the world’s second-largest mercury exporter, and even highly educated and well-traveled Canadian professional geoscientists and engineers in the mining industry remain unaware of the problem’s scale. For many years, Rob Stevens, P.Geo., FGC, was one of those people. He has worked in the industry for 25 years and has

Poverty drives many artisanal gold miners, including those working the “ traditional ” El Alacran Mine, in Córdoba, northern Colombia. Artisanal miners often use ore-processing methods that release mercury in the ground and water. Few miners are aware of the dangers. P hoto : Kylie Williams P revious page : Continental Gold, which operates the high-grade Buriticá project in Colombia, has signed sub-contracts with small-scale mining associations representing about 200 local artisanal miners. The company helps the miners mill their ore and commercialise their gold. P hoto : Continental Gold

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