The Berkeley Pit in Butte, Montana, has been a source of environmental concern for decades, as its waters—highly acidic and teeming with toxins—have seeped into the surrounding area. But today, this once-deadly pit is being viewed through a different lens: a potential treasure trove of rare earth metals.
From Liability to Opportunity
The story of the Berkeley Pit begins with the mining boom in Butte, which saw extensive copper extraction, leaving behind large quantities of toxic water in the pit after the mine closed in 1982. For years, the pit’s acidic waters, filled with harmful chemicals, posed a serious threat to wildlife and the local ecosystem. Yet, the very composition of the pit, rich in metals like copper, zinc, and rare earths has now become an unexpected opportunity.
According to the NYTimes, Montana Resources, the mining company that now operates in the area, has found a way to harness this water, extracting valuable metals through a process known as cementation.
This kind of alchemical trick uses scrap iron to transform copper-laden wastewater into pure copper. The company pipes liquid from the Berkeley Pit and cascades it over piles of scrap iron, a method that efficiently pulls copper out of the acidic brew.
Rare Earth Elements in Wastewater
Rare earth elements (REEs) are crucial for the production of powerful magnets used in electric vehicles, medical devices, and defense technologies like missiles and satellites. In fact, a single F-35 fighter jet uses 900 pounds of rare-earth metals.
One of the most promising opportunities lies in wastewater, which researchers believe could contain trillions of dollars’ worth of metals. “Water is the ore body of the 21st century,” remarked Peter S. Fiske, director of the National Alliance for Water Innovation at the Department of Energy’s Lawrence Berkeley National Lab. With new technologies emerging, scientists are now able to “pick through the garbage piles of wastewater and pick out the high-value items.”
Also, researchers at Indiana University are investigating the possibility of mining rare earths from coal waste, including fly ash and coal tailings. Meanwhile, scientists at the University of Texas at Austin have developed specialized membranes that can separate rare earths from waste materials. These methods are faster, more economical, and environmentally cleaner than traditional mining.
Mining the Berkeley Pit for Rare Earths
Among the most valuable metals in the Berkeley Pit’s toxic waters are neodymium and praseodymium, two light rare earth elements that are essential for producing high-performance magnets. These magnets are used in a wide range of applications. In fact, the United States is increasingly concerned with securing its own supply of rare earths to avoid relying on China, which controls the vast majority of global production.
Mark Thompson, vice president of environmental affairs at Montana Resources, explained that by extracting rare earths from the Berkeley Pit, “We’re turning a giant liability into something that’s contributing to defense.”
A Cleaner, More Sustainable Alternative
Traditional mining of rare earths is a highly destructive process, often involving the displacement of large amounts of earth and the use of toxic chemicals. In contrast, the methods being developed at the Berkeley Pit and other sites offer a much cleaner and more sustainable alternative.
Paul Ziemkiewicz, director of the Water Research Institute at West Virginia University, has spent decades studying Berkeley Pit’s waters. He developed a method to extract rare earths from acid mine drainage by filtering sludge, which is then refined into pure elements. “One of the nice things about acid mine drainage is the concentrates we get are particularly enriched in heavy rare earth.”
If successful, the Berkeley Pit project could produce up to 40 tons of rare earths per year, making it one of the largest domestic sources of these critical minerals.