Deep in the pine-covered mountains of central Mexico, the Sierra Gorda region is echoing with the sound of drills and the hopes of miners. Here, in one of Mexico’s most biodiverse stretches, a dramatic surge in illegal gold mining has triggered what locals and experts are calling a “mercury boom.” The price of mercury—a toxic metal vital to extracting gold from ore—has skyrocketed, transforming the region’s centuries-old artisanal mines into a lifeline for thousands of families, yet simultaneously endangering the health of miners, their communities, and the environment.
According to The Associated Press, the price of mercury in towns like San Joaquin in the state of Queretaro has soared from just $20 per kilogram in 2011 to between $240 and $350 by September 2025. This tenfold increase is tied directly to the soaring international price of gold, which has made mercury a hot commodity for illegal mining operations, especially in the Amazon basin. “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 studied mercury mines in central Mexico for years.
The process of extracting mercury from the earth is grueling and hazardous. Miners like Hugo Flores burrow deep into narrow mountain tunnels, following veins of cinnabar—the ore that holds mercury. They lug heavy bags of stone to the surface, where the rock is shoveled into wood-fired brick ovens. The mercury vaporizes, then cools and condenses into droplets of silver liquid, which are collected in small plastic Coca-Cola bottles. Each bottle can fetch about $1,800, but it takes a ton of rock just to produce a single kilo of mercury.
Mexico is now the world’s second-largest mercury producer after China, yielding an estimated 200 tons annually, as reported by the United Nations. This mercury is trafficked primarily to Colombia, Bolivia, and Peru, fueling illegal gold mining in the Amazon and contaminating vast swathes of rainforest. In July 2025, Peruvian authorities seized a record-breaking shipment of four tons of mercury—worth roughly half a million dollars—hidden inside bags of gravel en route from Mexico to Bolivia, AP reported.
Buyers, sometimes called “coyotes,” travel from around the world to purchase mercury cheaply from Mexican miners. “They come and buy mercury for 500 pesos, and then sell it in Peru for 5,000,” said Carlos Martínez, a leader of one of San Joaquin’s mines. “The coyotes, as we call them, they’re the ones that make money at the expense of others.”
Mercury mining in the Sierra Gorda is nothing new. The region’s mines date back centuries, and the metal was once used in everything from thermometers to cosmetics. But as global health concerns mounted, many countries banned the use and export of mercury. Today, the vast majority of Mexican mercury is smuggled to South America, where it is used in illegal gold mining—operations that are increasingly controlled by criminal groups.
A July 2025 report by the Environmental Investigation Agency, a nonprofit watchdog, alleged that the Mexican Jalisco New Generation Cartel has entered some mercury mining operations. However, miners, researchers, and local officials strongly deny cartel involvement, saying such claims unfairly criminalize vulnerable workers. “What we’re doing isn’t a crime,” Martínez insisted. “We’re just working.”
For many in San Joaquin, the choice is stark: migrate to the U.S. or work in the mercury mines. Government figures show that nearly half of the town’s 8,000 residents live in poverty. Flores, the miner, recounted how his family migrated to the U.S. when he was a toddler, but after being denied a green card at 24, he returned to the mines, following in his grandfather’s footsteps. With the mercury boom, he’s seen more young men return from the U.S. to work in the mines. “We’re forgotten by the Mexican government,” Flores said. “With the job opportunities out here … you can barely make ends meet.”
About 3,000 people in the region depend on the mines or their recycled materials, according to Izarelly Rosillo, a lawyer and researcher at the Autonomous University of Queretaro. Rosillo has spent so much time with miners over the past 12 years that she was diagnosed with mercury poisoning herself. “Mercury has set off a wave of development in the region,” she said. “Though that comes with collateral damages.”
The health consequences of mercury exposure are severe and well-documented. Researchers and doctors have observed dangerously high levels of mercury in the environment and in miners. Symptoms include tremors, neurological decline, vision and hearing loss, and developmental delays in children. Rosillo herself reported brain inflammation, hearing loss in one ear, depression, and tremors—her blood tests showed mercury levels twelve times the normal limit. Many miners, suffering from tremors and slurred speech, often attribute their symptoms to Parkinson’s disease, though studies have linked such conditions to mercury exposure.
Samuel Ledesma, who began working in the mines at age 12, described how his body began to shake and gradually deteriorated. “I ended up being sick for life,” the now 75-year-old said. Despite his condition, he remains skeptical about the full impact of mercury on miners’ health—a sentiment echoed by others in the community.
The environmental toll is equally alarming. The Sierra Gorda Biosphere Reserve, a protected area home to endangered species such as jaguars, military macaws, and Mexican black bears, is now considered “the most contaminated place in Mexico,” according to Díaz-Barriga. “This region isn’t just polluted. It’s poisoned.” Mercury contamination has seeped into sediments, trees, and waterways, threatening the delicate balance of this biodiversity hotspot.
International efforts to curb mercury mining have had mixed results. In 2017, Mexico was among 152 countries to sign a U.N. convention banning mercury mining and making exports illegal. Artisanal mines like those in Queretaro were given until 2032 to close, but this has thrust miners into a legal grey area. As global mines shut down, demand for Mexican mercury has only increased. In 2021, Mexico and the U.N. created a fund to help miners transition to new industries, but miners say they have yet to receive meaningful support. “Any alternative job won't match what they earn from mining mercury,” miners contend.
Mexico’s environmental agency stated it had conducted basic studies for a program to transition miners away from mercury and was actively working to “combat illegal trafficking.” The UN Environment Programme acknowledged “security risks in some mining areas” have “created delays and frustrations for affected communities,” but said authorities are working to speed up implementation.
As economic instability persists, miners worry the mercury boom will attract the attention of organized crime, especially as drug cartels have begun to push into Queretaro. “It’s easy for the Mexican government to say, 'We’re gonna close down the mine and we’re going to wash our hands of it,” Flores said. “That’s when organized crime is going to come in, because then it’s going to be the black market.”
The mercury boom in Mexico’s Sierra Gorda is a story of survival, sacrifice, and unintended consequences—a testament to the tangled relationship between global markets, environmental policy, and the lives of those caught in the middle.