In the pine-covered mountains known as the Sierra Gorda – one of the most biodiverse stretches of Mexico – a “mercury boom” is underway.

Soaring international gold prices are driving up the price of mercury, a toxic metal key for illegal gold mining, to all-time highs.

While the demand triggers a mining rush in central Mexico, sustaining thousands of miners and their families, it also exposes them and the fragile environment to mercury poisoning. At the same time, this Mexican mercury is fueling illegal gold mining in the Amazon, contaminating large areas and harming both people and the environment.

Global efforts to ban mercury mining have only made mercury from these centuries-old artisanal mines even more sought after.

In towns like San Joaquin in the north-central state of Queretaro, the price of mercury has skyrocketed more than tenfold over the past 15 years, jumping from $20 per kilogram (2.2 pounds) in 2011 to between $240 and $350.

Miners follow veins of cinnabar – the ore holding mercury – through narrow tunnels zig-zagging deep below the mountain. They carve into the rock and lug bags of stones strapped to their backs to the surface.

The rock is shoveled into wood-fired brick ovens where the mercury heats into a gas and separates from other minerals. The gas then cools into droplets of silver liquid that slowly drip down a pipe to be collected in small plastic Coca-Cola bottles, each of which sells for around $1,800 a pop. It takes a ton of rock to produce a kilo of mercury.

Mexico is the world’s second-largest mercury producer after China, yielding 200 tons a year, according to estimates by the United Nations.

Buyers come from around the world to scoop up mercury for cheap from artisanal miners.

Mercury mining in towns dotting Mexico’s Sierra Gorda region dates back centuries. The metal was used in everything from thermometers to cosmetics and legally shipped to South America up until a few years ago, when many countries around the world banned its use. Today, the vast majority of Mexican mercury is trafficked to Colombia, Bolivia and Peru and distributed throughout the Amazon basin.

In the Amazon, the metal is used to extract gold from river soil in illegal gold mining operations increasingly controlled by criminal groups. The mining has tainted the rivers that bring life to the region.

In July, Peruvian authorities seized a record-breaking shipment of four tons – worth about half a million dollars – of mercury hidden inside bags of gravel headed from Mexico to Bolivia.

A report by the Environmental Investigation Agency, a nonprofit watchdog that investigates environmental crime, said the Mexican Jalisco New Generation Cartel has entered some mercury mining operations in Mexico, miners, researchers and local officials say there's no cartel involvement, and suggesting otherwise has criminalized vulnerable workers.

“What we’re doing isn’t a crime,” said Carlos Martínez, a leader of one of San Joaquin’s mines. “We’re just working.”

The demand for gold is expected to continue as investors seek its tangible safety at a time of global economic uncertainty triggered by the Trump administration’s tariffs, according to J.P. Morgan and other banks. Miners say they expect the same for mercury.

Around 3,000 people in the region live off the mines or their recycled material, said Izarelly Rosillo, a lawyer and researcher at the Autonomous University of Queretaro. She has spent so much time with miners over the past 12 years that she was diagnosed with mercury poisoning herself.

Fernando Díaz-Barriga, a medical researcher who has long studied mercury mines in central Mexico, said that while authorities have not comprehensively studied just how deep the mercury poisoning runs, initial tests done by scientists show sky-high levels of the chemical in the environment and workers.

Miners often insist they haven’t felt the negative impacts of long-term exposure. Instead, they attribute the decline they’ve seen in fellow miners to Parkinson’s disease, which has been linked to mercury exposure in numerous studies.

Scientists, environmentalists and authorities at the United Nations also worry that the metal will wreak environmental destruction in one of the most diverse protected areas of Mexico: the Sierra Gorda Biosphere Reserve.

The mines are buried inside and adjacent to the reserve, which spans dense jungle and high altitude forest.

It’s considered a hot spot for endangered species, including the jaguar, military macaw, Mexican black bear, and hundreds of other species that scientists say could be affected if the mining isn't stopped and cleaned up by authorities.

International efforts to stop mining and the international trade of mercury have fueled criticisms that it’s only driven mercury demand in Mexico and put miners in the crosshairs of organized crime.

In 2017, Mexico was among 152 countries that signed a U.N. convention banning mercury mining and making all exports of the mineral illegal.

It gave smaller artisanal mines like those in Queretaro until 2032 to shut their doors, thrusting the mines into a sort of legal grey area.

As the world’s biggest mercury mines closed in recent years, miners in the Sierra Gorda say more buyers turned to Mexico as a source.

Mexico and the U.N. opened a fund in 2021 to provide workers with resources and training in new industries, but years later miners say they haven’t received a cent. And whatever job they change to will never match what they earn mining from mercury.

In a written statement, Mexico’s environmental agency said it had conducted basic studies for a program designed to transition miners away from mercury and that it was actively working to “combat illegal trafficking.” However, it declined to comment on accusations that it had failed to assist miners.

AP Video by Teresa de Miguel

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