Mercury-free concentration methods Mercury mixes with materials containing gold, forming an amalgam of mercury and gold that is then heated and vaporized to obtain gold. This process can be very dangerous and cause significant health risks and exposure to mercury. In mines, mercury is used to recover small pieces of gold that mix in soil and sediments. Mercury and gold settle and combine to form an amalgam.
The gold is then extracted by vaporizing mercury. Small-scale gold mining has been taking place in the Amazon for decades, with an enormous expansion of this activity since the early 2000s. It is often done by dredging rivers, in which miners excavate sediment in search of small pieces of gold. To separate gold, miners mix liquid mercury with the sediment, which forms a layer around the gold.
After the mercury is burned, what is left behind is solid gold, which makes up 20 percent of all the gold on the world market. First, mercury mixes with materials containing gold. An amalgam of mercury and gold then forms because gold will dissolve in mercury while other impurities won't. The gold-mercury mixture is then heated to a temperature that will vaporize the mercury, leaving the gold behind.
This process does not result in 100% pure gold, but it removes most of the impurities. Mercury is cheap and easily available to miners. It is used in varying quantities and for various purposes in the ASGM, depending on factors such as regional geology, cultural preferences and scale of operation. 3 One of the most dangerous and widely used practices is a technique called amalgamation of whole minerals.
The use of mercury to extract gold has become a key part of the survival strategy of millions of the world's poor, as gold prices have skyrocketed in recent decades. Sweeping consists of moving sediments that may contain gold into a curved tray with water and moving in such a way that the gold settles on the bottom while water and other particles leave the tray. Gold is heavier than most other particles, so alternative methods usually use motion or water to separate gold from lighter particles. Mercury extracts gold particles from crushed ore to form an amalgam (an alloy) of mercury and gold.
To help artisanal gold miners eliminate the use of mercury in gold mining and reduce harmful risks to their health and the environment, the GEF recently approved the Global Opportunities for Long-Term Development (GOLD) program in the small artisanal gold mining sector program, as part of the GEF's work in the focus area of chemicals and waste. However, illegal, small-scale gold mining operations sometimes use mercury to separate gold from other materials. In the socio-economic and political conditions found in small-scale gold mining operations, the use of mercury is often considered to be the easiest and most cost-effective solution for separating gold. Mercury has long been used in artisanal and small-scale gold mining (ASGM) to extract gold from mineral sediments and rock deposits.
The small-scale artisanal gold mining (ASGM) sector exposes miners to toxic mercury when they use the chemical to extract gold from the ore. Through the GOLD program, the GEF will provide funding to countries with an important gold mining sector and where many artisanal miners still rely on mercury for gold mining.