Solve pollution. Save lives. Protect the planet.

Meet Filipino gold miners Leoncio Na-Oy (pictured below, right) and Rudy Onos. Over the past few years, Pure Earth has been working with Leoncio and Rudy to test and teach a century-old, traditional method of mercury-free gold mining Leoncio rediscovered in his hometown in Benguet in the Philippines.

Leoncio and a friend arrives in Peru, in high spirits, for the latest round of mercury-free trainings.
Leoncio and Rudy arrives in Peru, in high spirits, for the latest round of mercury-free trainings.

From Indonesia to Senegal to Peru, the majority of artisanal and small scale miners around the world use toxic mercury in the gold mining process. As a result, artisanal and small scale gold mining is the leading cause of mercury pollution in the world, accounting for over 30% of global emissions.

But Leoncio knew there had to be a better way. He had turned to gold mining when he was unable to find a job after graduation. With a degree in history, Leoncio looked to the past for a solution and found it. Today, he is a vocal supporter of mercury-free mining, working to spread the word to fellow miners in the Philippines and beyond.

Leoncio has travelled to Bolivia and Mongolia with Pure Earth to train miners, and recently, he found himself in Ollachea, Peru.

Welcome to the Ollachea Community Mine
Welcome to the Ollachea Community Mine

This mining site, nestled in the mountains, is actually shared by about 15 different groups of artisanal miners, each with their own sources of ore and equipment.


Everyone here uses mercury, except for one miner.

Jose wanted to mine like the ancient Inca. So he has gone against convention and is proudly mercury-free. But he has one problem he hopes the Pure Earth team can help him solve. (More on Jose later.)

Jose shows off his technique
Jose shows off his mercury-free technique to Leoncio and Rudy.

Worldwide, some 15 million miners (including 4.5 million women and 600,000 children) toil at mines like this to make a meager living.

At this site, we saw both men and women share the work, at times with children nearby. All are exposed to toxic mercury every single day.



When you think of gold mining, do you think of holes dug deep into the earth using big machines? In fact, for artisanal and small-scale gold miners, a lot of the work happens above ground, in a time-intensive, multi-step process, using simple tools and contraptions that miners often build themselves.

The steps to extracting gold are similar the world over but with variations, depending on the terrain, the quality of ore, and other factors.  Because different methods are viable in different mining locations, Pure Earth is exploring a variety of techniques to reduce mercury that can be used in mines globally. Here is what artisanal gold mining can look like:

Step 1: Crushing the ore

There is gold somewhere in the piles of ore laid out here on the ground. The first step towards finding that gold is to crush the ore.



The ore is placed in a ball mill (like the one below) –  a barrel-like machine filled with metal balls – and rotated until the ore is crushed into a fine powder.

Step 2: Processing The Crushed Ore

  •  For most artisanal gold miners, step 2 involves the use of toxic mercury.  

At this mining site, ore is placed under large boulders along with toxic mercury. A man then stands on the boulder, rocking back and forth, sometimes for hours. This force helps to bind the mercury to the gold, creating an amalgam.


Crushed ore is funneled under the boulder, with mercury
Crushed ore is funneled under the boulder, with mercury

During this process, poisonous mercury is released into water and air. In such close proximity, the miners are all exposed to danger. They wear no protective gear except hard hats, and use their bare hands to sift the water and handle mercury.

  • In Leoncio’s mercury-free method, Step 2 involves sluicing, with NO mercury,

Without the help of mercury binding the gold, Leoncio teaches the miners to separate gold from the crushed ore by sluicing.

This is done in a contraption that Leoncio helps the miners build, that includes a sluice box and several chutes.


When completed, the various pieces fit together like a water slide.

At the start is the sluice box, which holds the grey-colored crushed ore. Leoncio fills it with water and starts the sluicing demonstration.


As the water washes the ore from the sluice box down a series of chutes, gravity pulls the heavier gold bits down, while lighter waste material washes away.



The heavier bits of gold settle at the bottom of the chutes.


In Peru, miners line the bottom of the chutes with pieces of felt cloth to help catch the tiny flecks of gold. In Indonesia, miners sometimes use a natural fiber called ijuk, instead of cloth, to line the bottoms of the chutes.


Step 3: Washing The Cloth

After several sluicing runs, the cloth is carefully removed from the chutes and rinsed in tubs of water.


Step 4: Panning

With a concentration of gold bits now in these tubs, it is time to pan.




Voila! A bag of gold.



Step 5: Smelting

Before smelting, Leoncio adds non-toxic borax to the gold mixture to help lower the melting temperature.

A crowd of miners gather around to watch the final step.



What Leoncio ends up with is 11.64 grams of gold.


Miners who use mercury are smelting too, but the key difference is that they are smelting the amalgam of mercury and gold that they produced earlier by rocking back and forth on that boulder.

In burning off the mercury to release the gold, they also release copious amounts of toxic mercury into the air. Some miners use a simple retort with a water condenser (like the one below) that can recapture some, but not all, of the mercury.


The photo below shows the difference between the gold recovered using mercury (left), and without mercury (right).


Remember Jose?

The miner who wanted to follow the Inca way? Leoncio and Rudy visited Jose’s mercury-free workshop and found many similarities.  But Jose had never been able to extract extra fine gold out of his crushed ore. With Leoncio’s method, however, Jose finally succeeded.


Looks like Jose will only have to make slight adjustments to increase his gold yield, all without having to use mercury.

At the end of the day, the miners proudly showed off the results of their hard day’s work.

SAM_2852SAM_2848 SAM_2846

About 10 to 25% of the world’s gold comes from artisanal mines like this one.


US Flag Color High

Pure Earth is working in Peru on a project funded by the U.S. Department of State to assist the Peruvian government and civil society in assessing artisanal gold mining sites, planning remediation efforts and strategies for alternative livelihoods, and sustainably restoring affected natural resources. Partners include the Ministry of Environment (MINAM: Ministerio de Medio Ambiente) of Peru.

Pure Earth also works in many other artisanal gold mining areas around the world to reduce the impact of toxic mercury while maintaining livelihoods. Because different methods work at different sites, project teams test a variety of approaches; some that eliminate the use of mercury entirely, and others that use (and recapture) mercury.


Comments are closed.