Rare-earth elements, an essential part of our technology, are actually not rare. Widely distributed around our planet, they are found only in low concentrations that are difficult to extract from ore and to separate efficiently. Rare earths are used in products from cell phones to electric car motors to military aircraft and drones. And China controls nearly 90% of these elements that are produced and processed world-wide–-a supply chain and security situation that many consider unstable.
The set of 17 soft, silvery-white elements known as rare earths do not exist naturally in seams, like copper or gold. They came into industrial use only when researchers developed efficient separation techniques during the late 1950s and early 1960s. Separating the individual elements is difficult because they are extremely similar chemically and tend to stick together. Each of these elements has distinctive and useful chemical, electrical and/or magnetic properties. Dysprosium, for example, is highly heat resistant, so an important component of advanced semiconductors. Neodymium is valuable for exceptionally powerful magnets that can lift thousands of times their own weight (e.g., producing magnetic fields that exceed 1.2 tesla while ferric magnets typically exhibit fields of 0.5 to 1 tesla). Lanthanum is used in camera and refractive telescope lenses and cerium is an important chemical oxidizing agent and catalyst.
(Source: Ogasa, 2023, Science News)
Where to Find Rare Earths
Rare-earth ores occur in many types of rock, ranging from carbonates to granites, and are found in countries around the globe, notably Canada, Ukraine, and Greenland. The elements are mined from enormous open pits. Crushing and then concentrating the ore requires a large amount of water and produces voluminous waste. The mining industry has a history of environmental contamination from mining rare earths. Toxic and radioactive materials fill the waste, and when not handled properly, these can contaminate groundwater and soil.
The United States has only one large-scale mine for rare earths—the Mountain Pass Mine in California near the border of Nevada, about 53 miles (85 km) southwest of Las Vegas. (While driving east on I-15 I’ve seen this enormous mine many times—now I finally know the treasure it holds!) The host rocks are igneous and most of the rare-earth oxides occur in the mineral bastnaesite, a source of lanthanides including neodymium and cerium.
For a few decades during the mid-20th century, the Mountain Pass Mine was the world’s top source for rare earths. But by the late 1980’s, China was intensively mining these elements and selling them at lower prices. The economic pressure, combined with spills of wastewater containing radioactive material, and changing ownership with management mishaps leading to bankruptcy, contributed to many years when the Mountain Pass Mine did not operate. Mining resumed in 2017 under the current owner, MP Materials, with the concentrated ore sent to China for processing into individual components. Currently, around 15 percent of the world’s rare-earth elements consumed annually are mined at Mountain Pass.
The Mountain Pass Rare Earth Mine & Processing Facility is the only active and scaled rare earth mining and processing facility in the United States. (2022, Wikipedia)
The largest known rare-earth deposits occur in northern China’s Bayan Obo Mining District in Inner Mongolia, where the main host rock is dolomite. Early in the 21st century, large amounts of radioactive and arsenic-containing mine waste were dumped onto farmland and into local water supplies, including the Yellow River. In 2010, concerns about the environmental damage and the depletion of the rare-earth resource led to China slashing these exports by 40 percent. Prices soared and for a while, hundreds of illegal mines operated in China, while around the world, new investments in rare earth mines were made. Bayan Obo produced about half of the world’s rare earth supply in 2019. The region is one of the most heavily polluted places on earth, causing numerous health problems for the surrounding population.
Concerns around new mining are prompting many to call for an increase in recycling. Advances in recycling technology are making the extraction of rare earths more efficient and less expensive. E-waste and mine tailings, including from uranium ore and even gold-rush era mines, could also provide significant amounts of rare earths that had no value at the time of mining.
The Recycling Route
Recycling rare earths begins with the challenge of a necessary infrastructure to collect and sort e-waste. Unlike gathering aluminum cans to make new products out of aluminum, the rare earths are difficult to separate, since they are typically in tiny amounts and also mixed with other materials in touchscreens, magnets, and many other products.
Traditional rare earth recycling methods require strong acids like hydrochloric acid, or extremely high heat, which results in substantial energy demands. Fortunately, chemists and material scientists are developing smarter approaches that are less demanding of energy inputs and toxins. Ramping these more environmentally friendly methods up to a commercial scale is the challenge ahead. We will need a variety of approaches.
A microscopic partner, Gluconobacter bacteria, can naturally produce organic acids that pull some rare-earth elements from the fluorescent phosphors in lighting or spent catalysts used to refine petroleum. Other bacteria can metabolize rare earths to produce a protein that preferentially grabs onto these metals. Systems that take advantage of bacteria might eliminate the need for many of the chemicals typically used to separate rare earths. The bacteria aren’t as efficient as hydrochloric acid, but they degrade naturally.
An especially promising approach is to pull rare earths from the millions of tons of coal ash waste left behind in ponds and landfills at power plants—waste that is filled with contaminants like mercury, arsenic and lead that are polluting soil and water over vast regions. Although coal ash contains relatively low concentrations of rare-earth elements, tremendous volumes of this waste material are readily available–-researchers estimate two billion tons of coal ash are currently stored, with about 70 million tons of coal ash produced each year in the United States. Scientists estimate that coal ash could contain six to seven times the amount of rare-earth elements the country has in domestic reserves. In April 2024, the Biden administration announced a $17.5 million investment into projects to extract rare earths from coal waste. If efficient and economical methods are developed to separate the rare-earth elements, then trash will be turned into treasure!
Rare-earth oxides. Clockwise from top center: praseodymium, cerium, lanthanum, neodymium, samarium, and gadolinium (2005, Wikipedia)
Processing Problems
Deindustrialization in the United States has ended up strongly favoring China, the country that currently refines nearly 90% of the world’s rare-earth elements. The rare-earth extraction systems used by Chinese refineries are highly sophisticated and closely guarded national secrets; the government supports extensive research programs for the rare-earth industry. Additionally, key materials can be cheaper to produce, powered by an inexpensive labor force, and loose environmental regulations.
Tens of millions of dollars in financing to United States-based companies have been awarded to promote the processing of rare-earth elements and other critical minerals, including graphite, lithium, and cobalt for electric battery manufacturing. However, permitting delays and environmental concerns, as well as competition from cut-price Chinese minerals, have held back these projects.
The Las Vegas-based company, MP Materials, operating Mountain Pass Mine, began processing operations in 2023 with a focus on high-purity neodymium-praseodymium oxide, a primary ingredient in high strength permanent magnets. The next step is to manufacture rare-earth magnets—a process that could begin within a year or so, when the company will send magnets to General Motors as part of a supply agreement. It’s a great start.
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A future with more electric cars, shiny screens, and other technological products will need new rare-earth element mines. This future will also need recycling—an important tool for building a domestic supply chain that is economically, environmentally, and socially sustainable.
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Thank you for another interesting, timely article.
Thank you, Deborah! I appreciate your note.
Well done article thats sets a nice framework for discussing REEs
Great to hear — thanks, Dan!
Thank you for your attention to this area which will only accelerate. Where is “two billion tons of coal ash are currently stored”. Is it easily accessible?
Much of the coal ash in the US is stored in ponds (some unlined) and most is at mine and power plant sites in the eastern half of the US. When I did an internet search of “map of coal ash ponds in the us”, many maps appeared. Thanks for the comment!