Rare earth elements are critical to many industries—used in electric motors, medical imaging and diagnostics, oil and gas refining, and computer and phone screens. The 17 rare earth elements all have important uses and are now in the news, with China halting exports to the U.S. in retaliation for tariffs and talks of trading them in Ukraine for U.S. military support.

Rare earth elements aren’t in fact rare—but they are rarely found in concentrated, economically viable mineral forms.  And when they are concentrated into minerals, those minerals are found in deposits that are very much dispersed in isolated locations around the world, with sparse availability near the surface. That affects which countries can produce them—and control the market. 

In the late 1990s and early 2000s, for example, China ramped up production on its Bayan Obo rare earth element deposit and flooded the global market, undercutting prices from other mines around the globe, including the U.S., ultimately putting them out of business. “This left countries at the mercy of China as the primary source of rare earth elements,” says Jill VanTongeren, professor and chair of the Department of Earth and Climate Sciences. 

The rare earth minerals have a long geologic history, which explains their dispersed locations—and relation to geopolitics, she notes.

The surface of the Earth is remarkably fluid, VanTongeren says, with land masses moving around the globe over millions and billions of years. 

“Most of us are familiar with Pangea—the supercontinent that formed about 300 million years ago and that the current seven continents broke off from to form their present-day arrangement,” said VanTongeren. “But Pangea is only the most recent supercontinent. Throughout Earth history, there have been at least five major supercontinent cycles—periods when continents all come together and then spread back out again into different pieces. We think this process happens roughly every 500 million years.” 

As the continents moved apart, breaks called rifts formed where tectonic plates separated. Magmas generated during the early stages of continental rifting can contain unusually large concentrations of rare earth elements, which then solidify and crystallize into deposits.

“As the rocks are pushed apart, they decompress, causing melting. It’s kind of like taking the lid off a soda bottle, and the bubbles rise to the surface.” said VanTongeren. “Those early magmas contain the highest abundance of rare earth and other incompatible elements that then enter the crust, either erupting in volcanic centers or solidifying at depth.”

Some of these magmatic deposits come to the surface, while many others get recycled back down into the mantle over geologic time. Other deposits can end up still too deep to reach with current mining technology.

What is left are a relatively small number of known deposits that are accessible to mining. Nearly 70% of actively mined rare earth minerals are found in the Bayan Obo mine in central China, with smaller deposits in the U.S. Mountain Pass mine in southeastern California, and a few other countries, she says. 

Recognizing China’s market dominance as a national security risk, the 2021 Infrastructure and Jobs Act and U.S. Department of Defense invested in placing Mountain Pass back online to re-establish a domestic supply chain, although the process can take up to 10 years. The rare earth deposits in Ukraine could represent a substantial addition to the market, though their concentration, grade, and economic viability remains uncertain.

“Political boundaries and the desire to obtain access to mineral resources have been the source of economic and military conflicts throughout human history,” says VanTongeren. “This is likely to continue as the world shifts toward green energy and a greater dependence on rare earth elements in the future.”

Finding sources of minerals not immersed in conflict is implicit in her research, which has taken her all over the world, from a ship off the coast of Antarctica, to the platinum mines in South Africa, the High Atlas mountains of Morocco, and even a newly discovered lithium deposit in Maine. “It’s a fascinating area of study partly because it lies at the intersection of science, economics, and politics,” she says.

At Tufts, a Rock Collection for the Ages

Tufts University has its own treasure trove of minerals in the P.T. Barnum Mineral Collection, currently held in the basement of Lane Hall on the Medford/Somerville campus. Thousands of remarkably beautiful—and some rare—specimens can be found on display and stored away in cabinets, many of which were collected by P.T. Barnum himself from his travels around the world. 

“In the late 1800s, it was considered fashionable for many prominent individuals to accumulate their own natural history collections,” says Jill VanTongeren. “P.T. Barnum was one of the biggest collectors of the time. His collection of animals, plants, and minerals was among the first gifts to Tufts University and part of an endowment to establish Tufts as one of the major natural history museums in the country.” 

While it was moved to Lane Hall after the burning of the Barnum Museum of Natural History in 1975, the mineral collection has been growing over the years, including samples from VanTongeren’s own field work. The collection will move again this summer, to the newly renovated Bacon Hall, which will house the Department of Earth and Climate Sciences.

“My pie-in-the-sky vision is to set up a mineral gallery with both a permanent exhibit as well as pop-up exhibitions every semester highlighting minerals important for technology, related to other research at the university, or to global events,” says VanTongeren. “I’d like to help bring back Barnum’s vision of bringing the beauty of, and an appreciation for, the natural world to campus.”