Artisanal mercury mining in the Sierra Gorda Biosphere Reserve has destroyed the ecosystem and endangered the lives of miners. The federal government has announced a gradual shut-down of mercury mines, but there are few alternatives for miners in sight. Mercury has become the livelihood of many communities in Querétaro, despite the fact that the soil, the air and the water have been gravely contaminated.

CAMARGO, Querétaro. — A cascade of falling rock interrupts the harmonious landscape of the Sierra Gorda. While sunlight pours over the clouds and shines blissfully over a Virgin of Guadalupe painted on a mountainside, chimneys of smelting kilns pump out a sulfurous, pungent smog.

Wrapped with switchbacks, the Camargo mine is split among four hillsides where mercury is mined, processed and smelted using artisanal techniques. Emerging from the abyss of the mine’s entrance, three workers push a cart with sacks full of black ore. Their faces encased with soot, they are exhausted after spending hours pummeling rocks with pickaxes.

Santiago steers the cart. He has spent seven years mining mercury in the interior of the Sierra Gorda but is unaware of the metal’s practical application: amalgamating gold, an ounce of which is worth about 50,000 pesos (2,000 USD). From Monday to Friday, 7 a.m. to 3 p.m. Santiago delves 300 meters into the mine with a pick and shovel to gather “the dirt”, as he calls it. “It’s not easy,” he confesses with sweat beading on his forehead and his helmet lamp shining. 

The miners, experts in finding the metal, identifying the veins by touch as if they were blind, blowing the ore free with one hand and scooping it up with the other. “The fault line marks where the ore is, but it’s very scarce because these veins have already been heavily mined,” Santiago explains.

“How much do you extract in a day?”

“Very little. In two weeks’ time maybe we’ll end up with half a kilo of liquid mercury, one kilo at most. There’s not much metal left, we mostly dig up the earth left behind by those who mined here before us.”

Once the rocks leave the mine, they are loaded into the bed of a truck and, bouncing off each other like billiard balls, taken to the smelting kilns, where a rock crusher from the Hong Kongese company The Nile Machinery sits atop a mound of incinerated tailings.

No other option

In the Sierra Gorda, cinnabar—the mineral from which mercury is extracted—has been mined for more than 500 years. Cinnabar yields a bright, blood-red pigment called vermilion and according to the historian Adolphus Langenscheidt, pre-Hispanic cultures believed that miners worked in the underworld, directly in contact with the blood of the Earth. Mercury, the only naturally occurring metal that takes a liquid state at room temperature, was considered to be water charged with magical qualities.

Aligned in a row sloping downward from the mine’s entrance, the smelting kilns consist of brick ovens under improvised awnings. To rent a kiln and cover firewood costs, miners pay around 800 pesos (39 USD). “Here we melt the mercury, first it turns from stone to smoke, then from smoke to liquid,” Ernesto clarifies as if he were an alchemist.

Ernesto started working at the mine in March 2020 as a result of the pandemic. He says it is the most profitable line of work in the region. “Sometimes I travel to the city of Querétaro to work as an electrician. But my family is from here. We’re at home in the mine,” he says with beaming pride, “we’re not outsiders.”

“Who employs you at the mine?”

“We work independently.”

While an old man packs mud onto an adobe kiln to cover up fissures, Ernesto cracks rocks apart with a hammer. Vapors that condensed some 100 million years ago in the Cretaceous period are released when exposed to the 1,200°C-degree temperatures inside the kiln, separating the mercury from the sulfur. After five hours what was once rock is now burning lava. The released vapors condense and the resulting liquid mercury is collected into soda bottles.

The miners at Camargo often do not know what the mercury they mine is used for. “We sell it to intermediaries and they commercialize it,” says Pedro, who started working at the mine ten years ago, when he finished high school. “The mine is the livelihood of all Camargo, there is no other work. It’s either this or travel every day to Querétaro to work in construction, earning 2000 pesos and spending 300 in bus fare,” he says with a hint of indignation.

“Have you suffered adverse health effects?”

“Not a lot. We have special kilns and we don’t have problems. On some mountains they wipe the droplets, once we got really spooked, really nervous. I think entering the mine is more dangerous than working the kilns. And for 500 pesos (24 USD), getting sick isn’t worth your while.”

For a kilogram of liquid mercury, most commonly packaged in a 500 ml Coca-Cola bottle, miners receive between 500 and 700 pesos (35 USD). Producing 700 kilos of mercury can take up to two weeks.

Most kilns are located at the base of the mine where, according to a study carried out by the National Institute of Ecology and Climate Change (INECC) in August 2020, the concentration of airborne mercury has been measured at 129.7 µg/m3, twelve times higher than the level recommended by the World Health Organization. The same study indicates that “the environmental consequences of mercury mining include soil and water contamination . . . and the constant emission of mercury into the air.”

Along the winding roads of the Sierra Gorda, mercury can be found as easily as pulque on the highways in the State of Mexico or as roadside flowers in Morelos. A kilogram sells for 1,680 pesos (85 USD); vendors also offer stones of quartz and antimony that they gather to subsist.

According to estimates by Mexico’s Secretariat of the Economy, between 700 and 1,000 workers mine mercury in the Sierra Gorda region. In 2016, a year before Mexico adopted the Minamata Convention on Mercury, which bans the toxic metal, annual production reached 804 tons in the municipalities of Pinal de Amoles, Peñamiller, San Joaquín and Cadereyta de Montes, where gold, silver, antimony, lime, marble, gravel and semi-precious stones are also mined.

The federal government promised to offer alternatives to mercury mining but, despite the scientific observation of high contamination levels, the proposals have not yet become a reality. Furthermore, the lack of a management plan for mine waste leads to the piling-up of tailings, which can leach contaminants in an area of up to 100 km2.

On June 25, 2021, the federal government presented its “Project for transforming mercury mining in the Sierra Gorda of Querétaro”, which offered an analysis of the situation. “It is estimated that most mercury is sold informally and that Mexico has become one of the metal’s main exporters, shipping to countries like Bolivia, Peru, Colombia and Ecuador to be used in small-scale mining of gold and silver.”

Fernando Díaz-Barriga, a researcher at the Autonomous University of San Luis Potosí (UASLP), explains the transition of mining after Mexico’s adoption of the Minamata Convention. “When it was still legal, Mexico exported mercury to countries in South America. When Colombia prohibited the metal’s sale, Mexico sold to Peru and Bolivia, which were both legal markets where the metal is highly demanded for small-scale gold mining. How peculiar that artisanally-mined mercury is used for artisanal gold mining in rivers throughout the Amazon.”

“Can artisanal mercury mining be put to an end in Mexico?”

“China produces 90% of the world’s mercury. We don’t even compete. The day Mexico stops mercury mining, nothing will change. The Chinese will keep at it.”

“What alternatives exist for these communities?”

“The miners have to decide what they want. If not in the mine, they work in greenhouses spraying pesticides or at construction sites laying brick. The alternatives are just as precarious as mining.”

The article “Holistic health risk assessment in an artisanal mercury mining region in Mexico” published in the journal Environmental Monitoring and Assessment in July 2021 shows that concentrations of mercury in the air, water and soil, as well as in biota (plants, rodents and worms) and in people (children, women and miners) exceed healthy levels.

The Agency for Toxic Substances and Disease Registry (ATSDR) indicates that levels greater than or equal to 10 µg/m3 demand evacuation of the population. One of the measurements taken near a kiln at the La Soledad mine captured levels of 275 µg/m3, 26 times higher than the healthy limit.

“In this sense, the Minamata Convention should include biomonitoring programs, not only for humans but also for key ecological receptors in contaminated ecosystems,” suggests the article, co-authored by Díaz-Barriga.

Toxic exports

Mexico produces triple the mercury (63 tons) that Norway does (20 tons); however, its production levels fall far from China’s (3,600), the world’s top producer of the metal, which, in accordance with Minamata Convention, must halt all mercury mining by 2032. Up until 2021, China was South America’s primary mercury provider.

 Mexico has regularly sold mercury to the other member countries of the Pacific Alliance—Colombia, Chile and Peru—all three of which have also adopted the Minamata Convention to curb the presence of mercury in the environment. 

Since Peru’s mercury importing ban in 2015, Bolivia has occupied the slot as the world’s second-largest importer. “No regulations have been issued to control mercury imports,” says Oscar Campanini of the Bolivian Documentation and Information Center (CEDIB). “Bolivia signed the Minamata Convention but has never complied with it. While there is mounting pressure against importing mercury, it’s still legal.” 

Campanini contributed to the report Opening the black box: Local insights into the formal and informal global mercury trade revealed, developed with the support of the International Union for Conservation of Nature (IUCN), and he confirms that up until 2020 the majority of mercury imports to Bolivia originated in Mexico (93%), entering the country by land after first traveling to Arica, Chile by sea.

According to the General Import and Export Tax Law, exporting mercury requires a permit from the Federal Commission for the Protection against Sanitary Risks (Cofepris) and an authorization from the Environmental and Natural Resources Secretariat (Semarnat).

Bolivian customs records show 26 Mexican companies that have exported mercury. The Querétaro Miners’ Union, headed by Juan José Zamorano Dávila, has sent at least 56 shipments of liquid mercury. He also oversees Vesia Internacional, a company he founded with his partner Sandra Ceballos Parra in March 2019, which “imports and exports rocks and minerals, both metallic and non-metallic, in compliance with all applicable regulations.”

Mining Products RT, owned by René Reyes Santillán and Marisela Terán Alcántara, registers 19 shipments sent from the Pacific port of Manzanillo to Arica, Chile en route to La Paz, Bolivia. The company, founded in Ecatepec in the State of Mexico in November 2013, states its purpose as “purchasing, selling, distributing, importing, exporting, commissioning, consigning and marketing of materials, articles, equipment, spare parts, accessories, products and everything related to mining.” Reyes Santillán’s sons, Armando and Miguel Ángel, market and sell liquid mercury in Mexico and Colombia through the company Comercializadora Internacional Euromanantial, via the webpage www.mercurioqro.com, and on online sales platforms like Mercado Libre, where a kilogram of liquid mercury goes for 4,000 pesos (about 200 USD).

There are also companies like Solvitec México, established in 2011 and owned by Enrique Polo Madero, which states its purpose as “the purchase, sale, distribution and export of deposits containing metals or minerals of all kinds.”

In Zacatecas, Aldrett Hermanos, founded in October 2003, is a family business chaired by Jorge Luis Aldrett Lee and dedicated to the “purchase and sale of metals and minerals and all kinds of proprietary equipment for mining” as well as the “purchase, urbanization, subdivision of all kinds of non-rural land, including the construction of houses and their sale.”

 According to the 2022 Directory of Mining, six mining companies in Mexico actively extract mercury. Among them, Barite Pacific Corporation, with operations in the cities of Colima and Zimapán, Hidalgo, is owned by Erick Marte Rivera Villanueva, a national congressman of the PAN party. Records from the Secretariat of the Economy show that Villanueva also owns the El Tabaquito and La Minita mines, both in Coalcomán de Vázquez Pallares, Michoacán.

Other companies include Proyectos de Metales y Minerales Sony, eles de Zacatecas, Mercurio del Bordo and Minera Orca.

  Most mercury exports to South America set sail from the port of Manzanillo in the state of Colima, the same port where, on June 12 of this year, 20 containers with precious metals—including gold and silver—were reported stolen.

Reporting was made possible thanks to the GRID-Arendal Investigative Journalism Grant 2022 and the support of the Pulitzer Center’s Rainforest Journalism Fund.