The soaring price of gold is fueling a mercury boom in central Mexico

Carlos Martinez discards mercury rocks after baking them in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

SAN JOAQUIN, Mexico (AP) — A drill echoes through narrow tunnels deep within the mountain where miner Hugo Flores bores into rock in search of one of Earth’s most toxic elements. Buried in red stripes of minerals illuminated by his headlamp is mercury.

A boom in mercury mining is underway in Mexico's pine-covered mountains known as the Sierra Gorda – one of the most biodiverse stretches of the country.

The toxic metal is a key part of the process in illegal gold mining, and soaring international gold prices are also driving up mercury's price. 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.

Here are some takeaways from AP’s report on the issue:

Mercury's journey from central Mexico to the Amazon

Artisanal miners in Mexico’s Sierra Gorda extract mercury through a laborious process. They climb into narrow tunnels, carving out cinnabar-rich rock, and then carry the heavy bags of ore to the surface. The rock is then heated in wood-fired ovens, separating the mercury into a gaseous form that condenses back into a liquid. The mercury is collected in small Coca-Cola bottles and sold to intermediaries known as “coyotes” for around $1,800 a pop.

While many of the intermediaries are Mexican, others travel from around the world to buy low-priced mercury. Today, the vast majority of Mexican mercury is trafficked to Colombia, Bolivia and Peru and distributed throughout the Amazon basin.

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Hugo Flores looks at some samples of mercury ore, at the top, to calculate the cooking time in the furnace in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

Once in the Amazon, miners mix mercury with gold particles to create an amalgam. Then they burn off the metal, releasing a toxic vapor into the atmosphere. The remaining mercury often flows into rivers where it transforms into methylmercury — its most dangerous form — and builds up in fish and aquatic life.

What's driving demand for mercury in Mexico

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

The price of mercury in Mexico 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.

Experts say international efforts to curb mercury mining have inadvertently fueled demand for the toxic metal, as mercury miners in Mexico feel the pressure and buyers turn to the country’s small-scale operations as larger mines close down.

“Globally, the demand for mercury is only going to continue,” said Carlos Martínez, a leader of one of San Joaquin’s mines.

A region in peril

Scientists and researchers who have long studied the mercury mines in central Mexico say that the excavation of one of the world's most toxic chemicals is poisoning the miners who depend on the work to make ends meet.

Researchers interviewed by The Associated Press said they’ve watched the health of miners and their families deteriorate as they show some of the most severe symptoms of mercury intoxication, including tremors, neurological decline, vision and hearing loss, developmental delays in children and more.

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A miner checks for leaks in the pipes of a furnace where mercury is cooked in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

“For the first time in their lives, mercury is worth something, and the miners are saying: ‘It’s worth poisoning myself if I’m going to earn something,’” said Fernando Díaz-Barriga, a medical researcher who has long studied the mines.

Scientists, environmentalists and authorities at the United Nations also worry that the element 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.

The area around the mines “is the most contaminated place in Mexico,” Díaz Barriga said. “This region isn’t just polluted. It’s poisoned.”

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A flame rises from a traditional furnace where mercury ore is heated to turn it into liquid in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

A sample of mercury is displayed in a Coca-Cola bottle in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

A worker enters a mercury mine in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

Hugo Flores poses for a photo just outside the mercury main entrance in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

A worker emerges from one of the caverns while mining mercury in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

Workers shine headlamps on their colleagues as they emerge from one of the caverns of the mercury mine in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

A miner pulls sacks of mercury ore in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

Carlos Martinez prepares mercury ore before placing it in a furnace tube to bake in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

Mercury ore is mixed with a lime chemical powder to boost the combustion when it bakes to create mercury in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

Hugo Flores analyzes a rock recently extracted from the mine in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)

A miner analyzes a sample of sand and rocks to determine the amount of mercury ore before cooking it in San Joaquin, Mexico, Tuesday, Aug. 19, 2025. (AP Photo/Fernando Llano)