The road to sustainable rare earths runs through Brazil

In early 2024, a team of citizen scientists waded into a shallow, brown creek in northern Myanmar, an area controlled by an armed group aligned with the country’s military dictatorship. They collected samples from the stream to measure how the recent proliferation of rare earth mines had affected water quality.

Instead of digging, miners in this region drilled holes into the earth at the top of a hill and then poured in an ammonium sulfate solution to extract the metals—a technique called in situ leaching. In this process, rare earth ions swap places with ammonium as the solution slowly seeps through the soil and into large ponds at the bottom of the hill.

In most cases, these mines weren’t treating their wastewater. “They just discharged it directly to the creek,” says Tanapon Phenrat, a chemist at Naresuan University who trained the citizen scientists.

Nearby residents told the advocacy organization Global Witness that after the mines opened, fish disappeared from streams and the water caused rashes.

The results from the water sampling added evidence to those concerns, showing acidic conditions, high ammonium levels, and heavy metals inadvertently extracted from the clay during leaching.

“Everything is depleted,” a community member told the advocacy group EarthRights International, which helped coordinate the water sampling. “The land is now barren.”

Rare earth elements are used to make magnets for electric car motors, wind turbines, consumer electronics, and many other products. The magnets are mostly composed of the light rare earths neodymium and praseodymium. But to function at high temperatures, the magnets also need small amounts of the heavy rare earths dysprosium and terbium.

While mines in the US and Australia produce significant quantities of light rare earths, heavy rare earth mining is dominated by Chinese-owned firms operating in China, Laos, and Myanmar. These companies ship mixtures of crude rare earths to facilities in China, where nearly all heavy rare earths mined globally are refined.

Heavy rare earths are needed for technologies slowing climate change, but the leaching methods used to mine them have left a trail of devastation in Southeast Asia. Governments in North America and Europe are also concerned about China’s near total control of the industry, and they’re eager to develop mining and refining capacity elsewhere.

Some companies now claim they can produce heavy rare earths more sustainably and break the world’s dependence on China. They’ve set their sights on Brazil, which has clays similar to those found in Myanmar.

Instead of pouring chemicals into the ground, companies like Aclara Resources, Meteoric Resources, Serra Verde, and Viridis Mining & Minerals plan to dig up heavy rare earth–rich clays in Brazil and process them in centralized facilities. This method is more expensive but can ease the environmental damage associated with rare earth mining.

“We know the expectations,” says Hugh Broadhurst, Aclara’s chief operating officer. “Our potential customers . . . want a supply chain where they know where the material is coming from, where the heavy rare earths are coming from.”

China’s grip on rare earths tightens

For years, the main sources of heavy rare earths were leaching operations in southern China. Many of these mines were illegal and inflicted serious environmental damage on surrounding communities.

Around 2016, the Chinese government began cracking down and closed some of the most-polluting mines. Illegal miners responded by setting up shop in neighboring Myanmar, according to David Riley, a rare earth analyst at the research firm Wood Mackenzie.

“It’s still Chinese operated, or linked to Chinese firms,” Riley says. “It’s just taking place over the border now, in an environment where they don’t have the same . . . compliance requirements.”

Rare earth shipments from Myanmar to China started to surge after a military junta seized control of Myanmar’s government in 2021. That year, the number of mining sites in the region more than doubled, according to a report from the Institute for Strategy and Policy—Myanmar. Armed groups connected to the junta and local militias both use rare earth mining to fund their activities.

In 2025, mines in China, Myanmar, and Laos—most of them owned by Chinese firms—extracted 86% of the world’s dysprosium and terbium, according to the research firm Adamas Intelligence. All this ore was transported to China for separation. “China was the only show in town,” says Chris Williams, a rare earth industry analyst at Adamas.

China has used its tight grip on the rare earth supply chain as a weapon several times. In 2010, the country halted exports to Japan, causing a major price spike. More recently, China has clamped down on exports of rare earths to gain an upper hand in negotiations with the US, a move that led to production delays at car factories in the US and Europe.

US and European governments have started making major investments in rare earth mining and processing to reduce their dependence on China. For example, the US government took a $400 million stake in MP Materials, a California firm that extracts rare earths from hard rock, in July 2025. The investment could help shore up the country’s supply of light rare earths, but MP’s mine isn’t a significant source of heavy rare earths.

In March, the US Department of Defense agreed to buy $96 million of rare earth oxides (PDF) from Lynas Rare Earths, which owns a hard rock mine in Australia. Adamas reports that the Australian mine produces 4% of the world’s heavy rare earths—not enough to meet demand for magnets outside China.

In May, US president Donald J. Trump traveled to China to discuss trade policies, including access to rare earths. After the meeting, the US said China would address its concerns about shortages of some rare earth elements, but didn’t mention dysprosium or terbium.

Brazil has recently emerged as an alternative for companies and governments to source heavy rare earths outside Asia. Last year, the US International Development Finance Corporation offered Serra Verde a financing package worth more than half a billion dollars for its mine in Goiás, Brazil. And in 2024, the Export-Import Bank of the US announced that Meteoric’s heavy rare earth–focused mine in Minas Gerais, Brazil, had made it through an initial round of due diligence for a potential loan (PDF).

These miners say that opening heavy rare earth mines in Brazil will make it harder for China to use its control of the materials as political leverage. “Concentration of supply in a single jurisdiction is not just a commercial risk; it is a geopolitical vulnerability,” Serra Verde CEO Thras Moraitis said during an investor call in April.

A new process that avoids leaching

The soft, pinkish clay at Aclara’s planned mine in Goiás crumbles easily. It’s buried only 30 m below the surface, so the company can easily reach it without blasting or drilling. This type of soil, called ionic adsorption clay, contains a high proportion of dysprosium and terbium.

Miners value the clay not only because it contains heavy rare earths but also because the metals are easy to chemically extract. As the granite below the clay slowly weathers, it releases rare earth elements as ions that bind to the surface of clay particles.

This means companies don’t have to use rock crushers and strong acids to liberate the rare earths from their host minerals—necessary steps in rock mining operations like Lynas’s in Australia. “Mother nature has done all the hard work,” says Rafael Moreno, CEO of Viridis, which is developing a rare earth mine in Minas Gerais.

Viridis, Aclara, and other firms in Brazil plan to use an open-pit quarry process to dig up the clay. Trucks will transport the soil to a centralized processing facility, where it will be mixed with an ammonium sulfate solution.

In the same process that occurs during in situ leaching, ammonium ions are exchanged for rare earth ions in the clay. The liquid is washed out of the clay and mixed with ammonium bicarbonate or oxalic acid to precipitate a concentrated mixture of rare earths.

Risnsing the clay with water removes leftover ammonium sulfate, which is sent back into the processing plant. The companies return the washed and dried clay to the pits and refill the holes or store the material in stacks.

In 2024, Serra Verde’s mine became the first to start processing ionic adsorption clays this way. The company hopes to ramp up to 6,400 metric tons of mixed rare earth products by the end of next year.

Companies are devising a new way to get rare earths from ionic adsorption clays

Moreno argues that this method is safer than in situ leaching because potential pollutants stay contained. He says that it’s impossible to completely control the flow of chemicals injected into a hillside and that there’s always a chance they will leak into the environment.

Williams at Adamas Intelligence says miners in Brazil should have more success winning permits for central processing than for leaching operations. “In situ leaching is absolutely the cheapest way to do it, but it has heaps of environmental side effects,” he says. “And the social license aspect is pretty important.”

But mining heavy rare earths in Brazil will also be far more expensive. With no regulators looking over their shoulders, many miners in Myanmar skip costly measures to mitigate pollution. The state-owned mining firm that extracts heavy rare earths in China must abide by stricter regulations, but it still doesn’t have to build a centralized processing plant of the type proposed for Brazil.

The research firm Benchmark Mineral Intelligence estimates that using centralized processing for heavy rare earths could cost five to seven times as much as in situ leaching. Aclara’s project is expected to cost more than $780 million to build. “It is more expensive to do it right,” Broadhurst says.

Virdis and Aclara intend to make up for the higher cost of extraction by selling products at a premium to customers that want to separate their supply chains from China. Willis Thomas, a rare earth analyst with the minerals consulting firm CRU, says carmakers will probably pay extra for magnets made with non-Chinese materials, as heavy rare earths are a small fraction of their costs and having multiple sources insulates them from unpredictable policy changes. “We’re talking about trading off affordability and resilience,” he says.

Miners chase lower costs by making leaching safer

Some companies in Brazil are braving the regulatory risks of in situ mining, arguing that it’s the only way to build projects cheap enough to compete with Southeast Asia.

In the spring of 2025, Brazilian Critical Minerals (BCM) opened the taps on blue tanks filled with chemicals on a hill in the state of Amazonas. The solution flowed into pipes that delivered the leaching agent into the soil, marking the first test of in situ leaching for rare earths outside Asia.

BCM argues that the in situ method can be used responsibly. The firm will use magnesium sulfate instead of ammonium sulfate. Ammonium sulfate, which is typically used for leaching in Asia, is also a nitrogen-containing fertilizer, so it can cause excessive plant or algae growth if it flows away from the mine and reaches rivers and streams.

A 2025 study by researchers at Beijing University of Technology found that switching to magnesium sulfate can reduce nitrogen pollution and other types of environmental damage. But the method still carries pollution and human health risks.

BCM’s field test showed that flushing drill holes with water removed residual metals and that pH and magnesium levels returned to normal after 4 weeks, the firm says. “Our rare earth clays can be effectively neutralized and stabilized after leaching,” Managing Director Andrew Reid said in an October investor presentation.

Despite those claims, obtaining environmental approvals for the in situ process could be a battle. The company got permission from the Brazilian government to test it, but it’s still awaiting approval for commercial-scale operations.

Broadhurst, the executive from Aclara, said his firm didn’t consider in situ leaching because it would be too difficult to deal with the pollution and the regulations. “Even if you wanted to, I don’t see a regulatory pathway,” Broadhurst says.

Outside experts are also skeptical. Wood Mackenzie’s Riley says it’s hard to imagine in situ leaching working in countries with stringent regulations. The cost of such mining is low in Myanmar in part because no one pays for any remediation, which wouldn’t be the case in many other parts of the world.

“You’re essentially just pumping chemicals into the ground and kind of hoping that you can collect and collate them,” Riley says. “I don’t think there’s a way to do in situ leaching that would be environmentally friendly and risk-free.”

In April, BCM agreed to partner with Southern Alliance, which holds a major stake in an in situ leaching mine in Malaysia operated by MCRE Resources. MCRE claims to have state-of-the art controls to make its process more sustainable.

BCM says it hopes to emulate the process practiced in Malaysia, but MCRE doesn’t have a perfect track record. In November 2025, the Malaysian government forced it to halt operations after a river near the mine turned bright blue and officials recorded high levels of radiation. BCM, Southern Alliance, and MCRE didn’t respond to questions about their plans to make in situ leaching sustainable.

Refining capacity is the missing link

Getting heavy rare earths out of the ground is only the first step in a long process that turns rocks or clay into magnets.

The mixture of rare earths extracted at a mine must be separated into individual oxides using solvent extraction. China currently separates 97% of the world’s dysprosium, according to Benchmark Mineral Intelligence. The country is expected to still be processing 79% of it in 2031.

If Brazilian miners hope to secure premium prices, they’ll need to process their ore outside China. Aclara says it will solve this problem by building a solvent extraction plant in the US. Serra Verde—which is set to be acquired by USA Rare Earth as part of that firm’s strategy to build a rare earth supply chain outside China—could send its ore to France, where USA Rare Earth partner Carester is building a separation facility. Moreno says Viridis is talking with companies in Europe and the US about processing.

But Neha Mukherjee, a rare earth analyst with Benchmark Mineral Intelligence, says processing capacity for heavy rare earths isn’t keeping pace with plans for new mines—which means the world will depend on China, along with the mines in Myanmar and Laos, for heavy rare earth elements for years to come.

“The gap is not at a geological level,” Mukherjee says. “It’s at the refining and magnet manufacturing.”

Moreover, she says, it’s unlikely that opening more sustainable mines in Brazil will yield enough rare earths to slow unregulated mining in Myanmar.

Phenrat, the researcher who trained the citizen scientists in Myanmar, is trying to help locals contend with an industry that isn’t going away. While in situ leaching carries risks, he argues that that miners in Myanmar should at least be neutralizing acid discharge and collecting mine waste into tailing ponds—steps that helped clean up operations in China. “It’s not advanced technology,” he says. “They just don’t want to pay.”

The data gathered by the citizen scientists in Myanmar will give local authorities, mining companies, and residents a clear picture of how rare earth extraction is affecting the environment and help them decide how to manage the mines going forward, Phenrat says.

For the miners in Brazil, Myanmar is an example of how things can go wrong. They hope their projects will demonstrate that mining of heavy rare earths can be more sustainable.

“There’s an acknowledgement that it can be done,” Viridis’s Moreno says. “If we set the standard, the expectation is that everyone else needs to follow.”

Matt Blois is a food, ag, and cleantech reporter at C&EN.