Mercury and gold have a thing for each other. When combined, they attract and bind in a process called amalgamation. Naturally, when gold-seeking humans figured this out, it became a convenient way to separate liberated gold particles from the sand and other undesirables. Mercury has been used for the past fifty years in artisanal small-scale mining methods in roughly eighty countries, and its use is increasing. Between 1996 and 2002, a modern gold rush was triggered by a 10-fold increase in the price of gold, and other factors such as increasing poverty are driving more people toward gold mining, using whatever means available.
There are several ways that mercury is utilized by artisanal small-scale miners (ASGM). It may be mixed with concentrated ore through panning or added to sluices, ball mills or trommels in a process known as whole-ore amalgamation. The resulting amalgam of mercury/gold is called a prill, and it is roasted with a torch or over an open fire.
When the prill is heated, the mercury vaporizes and leaves behind a nugget of porous gold, often referred to as sponge gold. Whether the process takes place indoors or out, the effect is the same; the vapors are highly toxic when inhaled and lead to devastating health problems. The majority of the vapor enters the atmosphere where it contributes to widespread global pollution, turning up in lakes and rivers thousands of miles from ASGM sites.
Oftentimes, the leftover water used in ore concentration with mercury is released into streams and rivers, where it enters the soil and is consumed by microorganisms. This is where the process of biomagnification begins. Small contaminated animals are eaten by larger ones until you reach the most toxic suspects of all – top chain predators, such as tuna and marlin.
In 2013, the ASGM was identified by the United Nations Environmental Protection Agency (UNEP) as the largest contributor of mercury to the environment, accounting for 37% of total anthropogenic (manmade) mercury emissions to the atmosphere. Numbers like these directly contribute to the formulation of Minamata convention mandates and the fuel the imperative to scale down the human need for mercury.
A comprehensive overview of mercury use and its hazards was created by Jack Caravanos, Professor of Environmental Health and Research Director of Pure Earth. It can be viewed HERE.