BRASILIA – Brazil is turning to forensic science in its fight against illegal gold mining in the Amazon, one of the most damaging forces threatening the rainforest, Indigenous territories and local communities. The illicit trade has helped speed up deforestation while pushing mercury pollution to alarming levels across parts of the region.
At the National Institute of Criminalistics in Brasilia, federal police have built what is known as a “gold lab,” a specialized facility that gathers and examines gold samples collected from across Brazil.
Its mission is straightforward but highly technical: determine whether a new sample, such as gold confiscated during a police operation, originated in a protected area where mining is banned. The process is known as “gold fingerprinting,” a method that allows investigators to trace the source of gold with striking accuracy.
Experts compare gold tracing to reading a person’s DNA
Inside the lab, glittering flecks of gold are stored in tiny, coin-like containers. But their real value lies not in their shine, but in the scientific record they carry. As gold forms naturally in rock formations or riverbeds, it absorbs elements from its surroundings, including trace amounts of silver, copper and other minerals.
That chemical signature becomes its fingerprint. By reading it, investigators can test whether seized gold truly came from the location claimed by its owner or whether it was extracted illegally from an Indigenous territory or national forest. If the sample matches data already collected from a protected area, authorities gain crucial evidence of unlawful mining.
Gustavo Geiser, a federal police forensic specialist, said the technique has been under development since 2019 through partnerships with Brazilian universities. Investigators rely on advanced equipment including X-ray fluorescence spectrometry, scanning electron microscopy and laser ablation mass spectrometry.
“As we advanced, the forensic examinations became increasingly complex,” Geiser said. Still, he noted, the central question has never changed: “Where did this gold come from?”
If the forensics prove a gold sample was illegally mined, the information then helps police build a case and move forward with further investigations and possibly charges.
Criminals insert illegally mined gold into legal markets
Those involved in environmental crimes in the Amazon frequently resort to fraud to introduce their goods into legal markets, not just when it comes to gold but also for cattle and timber. Lately, a worldwide surge in gold prices has only spurred on the mining rush in the Amazon rainforest.
Amazon Mining Watch, a platform that uses satellite imagery to track mining, estimates that about 496,000 hectares (1.2 million acres) of rainforest have been cut down for mining since 2023, including some 223,000 hectares (551,000 acres) in the Brazilian Amazon.
Brazil’s Federal Court of Accounts, its top audit institution, said last year there was evidence indicating that mining permits granted by the National Mining Agency to small-scale miners were being used to pawn off gold extracted from protected areas in the Amazon.
Greenpeace, in its own independent report in May, based on publicly available records, satellite imagery and aerial surveillance, detailed how the scheme works.
On paper, an owner of a legally authorized mine in the Amazon would declare that tons of gold had been extracted at that mine.
However, satellite and aerial imagery would show that there had not been any activity at the site of the legal mine. Meanwhile, images of bordering Indigenous lands, where mining is banned, would reveal large-scale mining operations — a “ghost mine” scam as Greenpeace calls it.
A federal court in Para, a northern state severely impacted by illegal mining, issued an order this month for institutions like the Central Bank and the National Mining Agency to enact effective control and traceability of all gold, from the mines to the markets. Brazil’s federal prosecutors also filed a lawsuit against the National Mining Agency, seeking better oversight of mining permits.
Prosecutor André Porreca, who is leading the case, said the permits have become a front used “to launder gold extracted by criminal organizations from Indigenous territories and protected areas.”
Geiser, the forensic expert, says the Brasilia gold lab is an important piece of the puzzle that helps battle crime and strengthen global gold supply chains.
“Being able to state that it (gold) has a legitimate origin and therefore is valid for inclusion in a country’s or a bank’s financial reserves, I believe provides solidity not only to the market but also to the countries’ financial bonds,” he said.
There is no data on how many criminals the lab has helped put behind bars, but Geiser says crime networks have recently begun exploiting neighboring countries such as Venezuela, French Guiana and Suriname, to launder illegally mined gold. Samples from abroad have made it to his lab, where they have joined the constantly growing database, he said.
The growing crime has also forced regional countries to strengthen collaboration through the Amazon International Police Cooperation Center, headquartered in the Brazilian city of Manaus.
Illegal gold mining leads to devastating mercury contamination
The Amazon is the world’s largest rainforest and a key regulator of global climate, so anything that degrades it could accelerate global warming, researchers say.
A 2023 analysis by MapBiomas, a nonprofit that monitors land-use, said that over 90% of Brazil’s mining is taking place in the Amazon region, with nearly 40% of it illegal, in protected areas.
Though illegal gold mining is a relatively small driver of deforestation, compared to agriculture, the harm it inflicts on the environment is nearly impossible to reverse — especially because of the use of mercury to extract gold. Once the gold is separated, the mercury is released into the rivers, contaminating water sources and fish essential to Indigenous life.
A 2023 study by Fiocruz, a Brazilian science institute, said 21.3% of fish in Amazonian markets exceeded the World Health Organization’s safety limits for mercury levels — with children between 2 and 4 years old consuming mercury at levels up to 31 times the recommended maximum.
Brazil signed the U.N. agreement known as the Minamata Convention on Mercury, which commits it to eliminate mercury use in gold mining.
The Ministry of Mines and Energy published a draft this month on easing out mercury that’s up for debate, meant to take place until Aug. 7. Federal prosecutors have urged that Indigenous groups — the ones most affected by the contamination — be consulted, but that has not yet happened.
A total ban on mercury would both curb environmental contamination and also bolster forensics investigations, according to Geiser of the federal police, whose lab can detect any traces of mercury in its samples.
“It will make it even clearer that any mining using mercury … is illegal,” he added.
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