Toxic Pits: Hidden Treasure Troves for Rare Earth Elements

A tale is shared about miners who discovered copper cans in early mining-era dumps. According to them, wastewater from copper mining flowed across his land, transforming steel cans into copper.

The tale may not be entirely true, but the process is factual and is known as cementation. Montana Resource, which succeeded the Anaconda Copper Company, still employs this alchemical method in the operations at the Continental Pitmine in Butte, Montana.

Adjacent to the mine lies the Berkeley Pit, filled with 50 billion gallons of highly acidic and toxic liquid. Montana Resource channels this liquid from the pits to cascade down iron piles, converting iron into copper for production.

While there have long been methods for extracting metals from water, recent years have ushered in a global rush for metals—vital for manufacturing and technological advancements—leading to a new wave of extraction methods and processes.

Researchers are currently focusing on mineral-rich sources like wastewater, including saline water from desalination plants, oil and gas fracking water, and mining wastewater. Researchers at Oregon State University estimate that the saline water from desalination plants alone contains approximately $2.2 trillion worth of metals.

“Water is a mineral reservoir of the 21st century,” stated Peter S. Fisuke, director of the National Water Innovation Alliance in California at the Department of Energy’s Lawrence Berkeley National Laboratory. “Today’s technology allows us to gather wastewater and extract valuable resources.”

There is extensive research dedicated to recovering rare earth elements—metallic elements sought after due to their increasing demand—from waste. For instance, researchers at Indiana Geological Water Survey at Indiana University are Mining rare earths in coal waste which includes fly ash and coal tails. Additionally, researchers at the University of Texas Austin have created membranes that imitate nature for Separating rare earths from waste.

Utilizing mining wastewater is not only quicker and more economical than establishing a new mine, but it also generates lesser environmental impact.

The vast, contaminated reservoirs in the pit near Butte contain two light rare earth elements (REEs): neodymium and praseodymium. These are crucial for creating small yet powerful magnets, medical technologies, and enhancing defense applications like precision-guided missiles and electric vehicles. Notably, an F-35 Fighter Jet uses around 900 pounds of rare earth metals.

“We’re transforming significant liabilities into assets that contribute to national defense,” remarked Mark Thompson, vice president of environmental affairs at Montana Resources. “There’s a lot of complex metallurgy at play here—the real cutting-edge science.”

This is a crucial moment for exploring domestic rare earth production. The U.S. currently lags behind China, and President Trump’s trade tensions have raised concerns that China may tighten its rare earth mineral exports in response to U.S. tariffs. Experts in mineral security at the Center for Strategic and International Research warn that this gap could enable China to accelerate its defense advancements more swiftly than the U.S.

The Trump administration is particularly fixated on Greenland and Ukraine due to their valuable rare earth deposits.

Trump has recently authorized the government to commence mining on much of the seabed, including areas in international waters, to tap into mineral wealth.

There are 17 distinct types of rare earth metals identified in the Berkeley Pit. While not rare in abundance, they are often deemed scarce due to their dispersion in small quantities.

Rare earths are divided into two categories: heavy and light. Heavy rare earths, including dysprosium, terbium, and yttrium, tend to have larger atomic masses, making them more scarce and thus typically traded in smaller quantities, leading to shortages. In contrast, light rare earths are characterized by a lower atomic mass.

Acid mine drainage is a hazardous pollutant created when sulfur-containing pyrite within rocks interacts with oxygen and water during mining. This process results in the formation of sulfuric acid, which poisons waterways. This environmental issue affects thousands of abandoned mines, contaminating 12,000 miles of streams across the nation.

However, acids facilitate the dissolution of zinc, copper, rare earths, and other minerals from rock formations, presenting an opportunity for extraction techniques that were not previously available.

Paul Ziemkievich, director of the Water Institute at West Virginia University, has been researching Butte’s pit water for 25 years. Alongside a team from Virginia Tech and the chemical engineering firm L3 process development, they developed a method to extract crucial metals from acid mine drainage originating from West Virginia coal mines, the same approach utilized in Butte. Large, densely woven plastic bags filled with sludge from the water treatment plant are employed, allowing water to seep through slowly and yielding about 1-2% rare earth preconcentrate, which requires further refining through chemical processes. The final patented step involves a solvent extraction method that results in pure rare earth elements.

“One of the remarkable aspects of acid mine drainage is that our concentrations are particularly rich in heavy rare earths,” explained Dr. Ziemkiewicz. “Light rare earths carry a lesser value.”

The Butte project is awaiting news on a $75 million grant from the Department of Defense, which is critical for enhancing rare earth enrichment and commencing full-scale production.

Zinc is also abundant in the acid mine drainage mixture and serves as an essential financial asset for the process as it commands a higher market price. Nickel and cobalt are also extracted.

Demand for rare earth elements is high; however, China dominates production, manipulating prices to maintain low costs and stifle competition. This is why the Department of Defense funds various projects focused on rare earth elements and other metals. The U.S. operates only a single rare earth mine in Mountain Pass, California, which produces roughly 15% of the global supply of rare earths.

The Berkeley Pit has posed a chronic problem since 1982, when Anaconda copper companies ceased their open-pit mining operations and halted water pumping, causing it to become filled with water. The acidity levels from the mine’s drainage have proven dangerous; in 2016, thousands of snow geese that landed in the pit quickly succumbed to poisoning, with around 3,000 birds reported dead.

The Atlantic Richfield Company and Montana Resources play crucial roles in permanently treating pit water to avert pollutioning the surrounding groundwater (Montana Resources operates the continental pit adjacent to the Berkeley Pit). The Clean Water Act mandates that companies manage acid mine drainage, and enhancing treatment capabilities at the local horseshoe bend plant is more cost-effective than developing a new facility, which may also offset treatment costs while boosting profits.

Numerous research initiatives have been launched to extract suspended metals from the water. Thompson displayed a map illustrating where radiation was emitted from Butte and where water samples have been dispatched to research facilities nationwide. However, the ongoing metal production process stands as the first to demonstrate profitability.

The mineral wealth present in this region has been recognized for many years; however, extracting it has proven challenging until Dr. Ziemkiewicz’s team innovated new methods. They generate rare earths from two coal mines in West Virginia, where acid mine drainage presents ongoing issues. Each of these mines yields about 4 tons of rare earths annually.

On the other hand, the Berkeley Pit is projected to produce 40 tons annually, bolstered by significantly higher concentrations of rare earths in solution and substantial water content. Dr. Ziemkiewicz believes that this method, when applied to other mines, could potentially satisfy nearly all domestic rare earth requirements for defense-related uses.

However, certain forecasts project that demand for rare earths may surge by as much as 600% in the next few decades.

Lawrence Berkeley laboratories are investigating technologies related to water filtration, particularly experimental approaches to improve membranes, as part of their overarching efforts to purify water, recover significant minerals, and produce necessary minerals. They operate a particle accelerator known as an advanced light source, which generates bright X-ray light that enables scientists to examine various materials at an atomic scale.

The lab has collaborated with external researchers to develop a new generation of filters referred to as nanosponges, designed to capture specific target molecules like lithium.

“It’s akin to an atom catcher’s mitt,” explained Adam Uliana, CEO of Chemfinity, a Brooklyn company exploring the use of nanosponges to purify a variety of waste. “It only captures one type of metal.”

In addition to rare earths, lithium, cobalt, and magnesium have gained significant attention from researchers.

Ion exchange, a well-established technology for extracting metals from water and purifying contaminants, is also gaining interest. Lilac Solutions, a startup based in Oakland, California, has developed specialized resin beads to extract lithium from brine via ion exchange, with plans for their first production facility in Great Salt Lake, Utah.

The company’s technology involves pumping brine through an ion exchange filter to extract minerals, returning water to its source with minimal environmental disruption. If this approach proves viable on a larger scale, it could revolutionize lithium extraction, significantly decreasing the necessity for underground mines and open-pit operations.

Maglathea Metal is an Auckland-based startup that produces magnesium ingots from the saline effluent generated by desalinating seawater. The company processes the brine, which consists of magnesium chloride salts, using a current powered by renewable energy to heat the solution, resulting in the separation of salt from molten magnesium.

CEO Alex Grant noted that the process is exceptionally clean, although it has yet to be applied to magnesium production. Much of the company’s work is funded by the Department of Defense.

With China accounting for 90% of global magnesium production, the current smelting process, known as the Pidgeon process, is highly polluting and carbon-intensive, involving heating to around 2,000 degrees using coal-fired kilns. Dr. Fisuke anticipates further innovations on the horizon.

“Three converging factors are at play,” he stated. “The value of these critical materials is climbing, the expenses associated with traditional mining and extraction are escalating, and reliance on international suppliers, particularly from Russia and China, is diminishing.”