University of Maine Geology Professor Chunzeng Wang, former Maine State Geologist Robert Marvinney and Maine Geological Survey Project Coordinator Amber Whittaker during a visit to Pennington Mountain on Oct. 16. Photo courtesy of Chunzeng Wang
Geologists have discovered a large concentration of rare earth elements and trace metals highly prized by the U.S. defense, technology and alternative energy industries in 450-million-year-old volcanic rock on a remote mountainside in northern Maine.
It is still too early to know the exact size and composition of the deposit, or whether it should or could be mined despite strict state regulations. But geologists say it may rival similar deposits discovered in Australia and China, and one estimated the potential value of the Pennington Mountain deposit in the billions of dollars.
These rare earth elements and trace metals of niobium and zirconium can be used to make a wide range of products: from night vision goggles to stealth technology, cellphones to flatscreen TVs and solar panels, to electric vehicle batteries to wind turbine generators.
The use of rare earth elements and trace metals in renewable energy technologies has fueled tensions in Maine and around the nation between the local environmental impacts of mining and the global climate benefits achieved through the use of those mined materials.
The owner of the land, located an hour’s drive northwest of Presque Isle in an unorganized territory, is Aroostook Timberlands LLC, a subsidiary of J.D. Irving, a Canadian company that has grown rich from oil, forestry and shipbuilding. With close to 1.3 million acres, it is Maine’s biggest landowner.
Irving didn’t respond to a request for an interview about the Pennington Mountain discovery.
The company has demonstrated a willingness to mine before, seeking to tap a zinc, copper, gold and silver deposit under nearby Bald Mountain. That effort fell short of the state’s strict mining and water quality laws, which it says make it virtually impossible to open a commercial metal mine in Maine.
Environmental and tribal groups claim that pit mines such as the one proposed for Bald Mountain – or a silver mine proposed east of Baxter State Park by the Wolfden Resources Corp. – could expose sulfide-rich rocks that would wind up contaminating the groundwater. The Wolfden project has been put on hold after the Ontario-based company faced rezoning challenges and some local opposition.
A Newry couple is trying to get the permits needed to mine lithium, a superconductive trace metal found in spodumene, from a large $1.5 billion deposit in western Maine, but so far the state has denied their efforts to classify the extraction as something other than metal mining. Lithium is in high demand worldwide to make rechargeable lithium-ion batteries used in electric vehicles.
Geologists have discovered rare elements and minerals in rocks on Pennington Mountain in Aroostook County, including niobium and zirconium, two Earth elements used in steel, jet engines and cellular phones. Photo by Chenzung Wang/Univeristy of Maine – Presque Isle
The questions of whether and when mining might be appropriate at Pennington Mountain are not priorities for the researchers studying the find.
“Mining is a story for another day, a future day,” said geologist Chunzeng Wang, a University of Maine at Presque Isle professor and lead author of a paper about the discovery in Economic Geology. “For now, it’s enough to know we have something essential to economic and national security right here in Maine.”
And there may be more where that came from, Wang said with a broad smile.
The Pennington Mountain discovery showed up as a bright red, 100-acre spot of elevated radioactivity in a 2021 image taken by a low-flying airplane during a magnetic and radiometric survey of a 3,800-square-mile swath of northern Maine that is about half the size of Massachusetts.
Although the radiation levels are not high enough to pose a threat to humans, it stood out like a giant “look here” sign in the middle of nowhere in the North Woods.
The aerial geophysical survey in northern Maine, which cost about $450,000, was part of the U.S. Geological Survey’s Earth Mapping Resources Initiative, or Earth MRI. It is conducted in a partnership with state geological surveys to hunt for critical mineral resources that have a particularly vulnerable supply chain.
So far, USGS has funded three focus areas in Maine: the Oxford lithium project in 2020, Pennington in 2021 and the geologic mapping of the Aroostook district, which is in the second year of a three-year hunt for manganese. Maine is the only New England state to get Earth MRI funding to date.
Initially, USGS believed the source of the radioactivity that lit up the scan was manmade, Wang said, like nuclear waste dumped there from the now-shuttered Loring Airforce Base in Limestone. A state geologist joked that it might be space junk that had fallen from the sky. Wang immediately volunteered to check it out.
Maine Geological Survey geologist Amber Whittaker called it a good example of scientific collaboration.
“Having all of us involved meant as soon as we identified the feature, Professor Wang was on-site within a day to do the recon work,” said Whittaker, who is the MGS project coordinator. In his Oct. 21 email to the group, on the day the initial geophysical survey was shared, Wang said: “I will find it out tomorrow.”
Geologists Chunzeng Wang, left, a professor at the University of Maine-Presque Isle, and Preston Bass walk through the woods at Pennington Mountain in Aroostook County. Geologists have discovered rare minerals in rocks on Pennington Mountain. Photo by Anji Shah/United States Geological Survey
The next day, Wang set out for Pennington Mountain, equipped with a hammer and a handheld radiometric sensor, to check the anomaly and collect samples in a cold October rain. Wang had mapped the area a year earlier and even then had hoped to study the ridge more.
Samples sent to a Nevada lab for chemical analysis would eventually reveal very high levels of trace metals like niobium, which is used to manufacture gas turbines, jet engines and MRI scanners, and zirconium, a corrosive and heat-resistant metal used in superconducting magnets.
Samples also contained high amounts of even more valuable rare earth elements and metals, including dysprosium, used to make magnets for electric vehicles and wind turbine motors; gallium, used in semiconductors for smartphones, light-emitting diodes and solar cells; and lanthanum, used in hydrogen fuel cells and electric vehicle batteries.
“I’ve been a geologist for many years now and I’ve never seen anything like it before,” Wang said. “Rare earth is misleading because they’re not rare. They can be found in many places, but in very, very small amounts. What is rare is to find a sizable amount of rare earth elements in one place. ”
Finding a sizable deposit doesn’t mean it can be mined, however. Rare earth finds have been identified in the U.S. but remain untapped because of water quality regulations and the high costs of compliance. As a result, the U.S. has only one active rare earth mine, Mountain Pass, in California’s Mojave Desert.
According to the USGS, China controls about 80% of the global output of processed rare earth materials. America imported an estimated 11,130 metric tons of so-called “rare earths” in 2018 valued at about $160 million, data shows. Eighty percent of that came from China, according to USGS.
“Rare earths are some of the most difficult metals to separate from a host mineral,” said USGS scientist emeritus John Slack of Farmington, who participated in the project. “You mine the ore, then crush it to get to the minerals, and then chemically separate it, sometimes multiple times, to get to the metals.”
Much of the rare earth elements mined in the U.S. is sent overseas to China to be processed before being shipped back stateside for use in domestic manufacturing. But the U.S. is trying to fix that – in 2021 and 2022, Pentagon officials announced $44.6 million in grants to build and run a U.S.-based rare earth element processing plant.
But, as Wang knows all too well, nobody in the U.S. really wants a mine built in their backyard. He told his university president and dean in a March email that Mainers should still celebrate the find, regardless of their thoughts about mining.
“Nobody likes mining in Maine, but it does not hurt if we know we have rocks that contain strategic and critical metals,” Wang said. “The rare earth elements and rare metals are all listed as USA’s strategic and critical metals/minerals, and they are essential to the economic and national security.”
The anomaly at Pennington Mountain was first detected as a bright red mound that appeared in data collected in aerial radiometric surveys conducted in 2021. United States Geological Survey
The Pennington Mountain find will likely lead to more aerial surveys of northern Maine, where USGS and Whittaker believe conditions are ripe to find other mineralized rocks created by a collision of ancient land masses during a time before the Atlantic Ocean even existed.
“The last time we flew over Maine was about 50 years ago, which gave us a broad-brush picture of what was there, like an impressionist painting,” USGS geophysicist Anji Shah said. Now, with GPS and high-resolution sensors, they have something more like a photograph, she said.
Wang believes the entire ridge at Pennington is rich in minerals, but Shah, who was in charge of reviewing the survey images, is more cautious. Handheld scanners only penetrate a few feet below the surface. Without digging, Wang could only sample surface-level rock outcroppings.
More study is needed at the site to determine how deep the mineral deposits run and how concentrated the rare earth elements and metals are within the mineral flakes threading through the rocks, Shah said. It would be up to the landowner or mineral exploration company to conduct such tests.
For now, the geologists are happy to celebrate the discovery that began with an unexplained red hot spot on a radiometric photograph snapped by a low-flying surveillance plane.
“This discovery shows just how much we still don’t know about the ground beneath our feet,” Shah said.
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