The world’s richest known lithium deposit lies deep in the woods of western Maine, in a yawning, sparkling mouth of white and brown rocks that looks like a landslide carved into the side of Plumbago Mountain.

Mary Freeman and her husband Gary found the deposit five years ago while hunting for tourmaline, a striking, multi-colored gemstone found in the region.

The Freemans make their living selling lab supplies through the Florida-based company they founded 40 years ago, Awareness Technology. But their true love is digging for gemstones, which has brought them for years to Mary’s home state of Maine, the site of some of the best tourmaline hunting in the world.

Since 2003, they’ve been buying up property parcels, studying core samples and old geological maps to determine where to try digging next, then spending hundreds of thousands of dollars a year on blasting and equipment. The couple has dug more than a mile of tunnels in pursuit of beautiful stones, and many of their finds—like blue elbaite and rich watermelon tourmaline—have wound up on display at the Maine Mineral & Gem Museum in nearby Bethel.

Now, the Freemans want to expand this pit, near the town of Newry, Maine, so they can mine spodumene, crystals that contain the lithium the U.S. needs for the clean energy transition. The timing of their discovery, in what has been named Plumbago North, is remarkable; the Freemans have stumbled across one of the only hard-rock sources of lithium in the U.S. at a time when the material is desperately needed for the clean energy transition. By 2040, the world will need at least 1.1 million metric tons of lithium annually, more than ten times what it currently produces, according to projections by the International Energy Agency. Should the Maine deposit be mined, it could be worth as much as $1.5 billion, a huge windfall for the Freemans and a boon to the Biden Administration’s efforts to jumpstart more domestic mining, processing, and recycling of critical minerals such as lithium, cobalt, and rare earth elements to reduce the U.S.’ dependence on China. This is one of the few lithium deposits in the U.S. currently found in hard rock, which means it is higher-quality and faster to process than lithium mined from brine.

“I consider myself an environmentalist,” says Mary, who on a recent rainy visit to the test quarry, was wearing jeans, a sweater, and hiking boots, her white hair pulled into a low ponytail. Most of the country’s critical minerals are mined elsewhere and processed in China, she adds. “I think [the U.S.] should try to be a little bit more self-sufficient.”

But like just about everywhere in the U.S. where new mines have been proposed, there is strong opposition here. Maine has some of the strictest mining and water quality standards in the country, and prohibits digging for metals in open pits larger than three acres. There have not been any active metal mines in the state for decades, and no company has applied for a permit since a particularly strict law passed in 2017. As more companies begin prospecting in Maine and searching for sizable nickel, copper, and silver deposits, towns are beginning to pass their own bans on industrial mining.

“This is a story that has been played out in Maine for generations,” says Bill Pluecker, a member of the state’s House of Representatives, whose hometown of Warren—a 45-minute drive from the capital city of Augusta—recently voted overwhelmingly in favor of a temporary ban on industrial metal mining after a Canadian company came looking for minerals near a beloved local pond. “We build industries based on the needs of populations not living here and then the bottom drops out, leaving us struggling again to pick up the pieces.”

Mainers often invoke the Callahan Mine in the coastal town of Brooksville as a warning. Tailings from the mine, which operated for several years in the late 1960s, were disposed of in a pile next to a salt marsh and creek. The former mine is now a Superfund site, and a 2013 study by researchers at Dartmouth College found widespread evidence of toxic metals in nearby sediment, water and fish. Cleanup costs, borne by taxpayers, are estimated between $23 million and $45 million.

“Our gold rush mentality regarding oil has fueled the climate crisis,” says State Rep. Margaret O’Neil, who presented a bill last session that would have halted lithium mining for five years while the state worked out rules (the legislation ultimately failed). “As we facilitate our transition away from fossil fuels, we must examine the risks of lithium mining and consider whether the benefits of mining here in Maine justify the harms.”

The Freemans’ point out that they plan to dig for the spodumene, then ship it out of state for processing, so there would be no chemical ponds or tailings piles. They liken the excavation of the minerals to quarrying for granite or limestone, which enjoys a long, rich history in Maine.

Advocates for mining in the U.S. argue that, since the country outsources most of its mining to places with less strict environmental and labor regulations, those harms are currently being born by foreign residents, while putting U.S. manufacturers in the precarious position of depending on faraway sources for the minerals they need. Though there are more than 12,000 active mines in the U.S., the bulk of them are for stone, coal, sand, and gravel.

There is only one operational lithium mine in the U.S., in Nevada, and one operational rare earth element mine, in Mountain Pass, Calif., meaning that the U.S. is dependent on other countries for the materials essential for clean energy technologies like batteries, wind turbines, and solar panels. Even after they’re mined, those materials currently have to be shipped to China for processing since the U.S. does not have any processing facilities.

“If we’re talking about critical metals and materials, we’re so far behind that it’s crazy,” says Corby Anderson, a professor at the Colorado School of Mines. “It’s the dichotomy of the current administration—they have incentives for electric vehicles and all these things, but they need materials like graphite, manganese, nickel, cobalt, lithium, and copper. The only one we mine and refine in this country is copper.”

The COVID-19 pandemic laid bare the problems of faraway supply chains; as U.S. consumers shopped online in their homes, the goods they bought, mostly from Asia, experienced lengthy delays at clogged ports. What’s more, diplomatic tensions with China motivated the U.S. government to seek other potential sources for mining, material processing, and recycling.

That’s why, in the pandemic’s aftermath, the Biden Administration launched an initiative to secure a Made in America supply chain for critical minerals. It included billions in funding for companies trying to mine and process critical minerals domestically.

The rocks in Plumbago North would seem to help provide a domestic supply chain for critical minerals; they are thought to be among the largest specimens of spodumene ever found, with crystals of such high quality that in addition to batteries, they could be used to make scientific glassware or computer screens, where the lithium metal would help lower the melting temperature.

The Freemans are just two of the hundreds of people prospecting for critical materials across the country as the U.S. tries to strengthen the domestic supply chain. According to an analysis by Patrick Donnelly, the Great Basin Director for the Center for Biological Diversity, a nonprofit environmental organization, more than 100 companies have staked claims for lithium deposits in the American West. Companies also have applied for permits to mine cobalt in Idaho, nickel and copper in Minnesota, and lithium in North Carolina.

Geologists say there’s also likely a lot more lithium in spodumene deposits across New England. Communities that haven’t had working mines in years may soon find themselves a key source for lithium and other minerals needed for car batteries, solar panels, and many of the objects people will need more of to transition themselves off polluting fossil fuels.

There are good reasons for U.S. communities to have healthy skepticism about mining projects; there is no shortage of examples of a company coming into a community, mining until doing so becomes too expensive, then leaving a polluted site for someone else to clean up. There are more than 50,000 abandoned mines in the western United States alone, 80% of which still need to be remediated. Passage of landmark environmental laws like the Clean Air Act of 1970 and the Clean Water Act of 1972 hasn’t made mining safe enough, environmentalists say.

“All mines pollute in one way or another, and mines are really bad at predicting how much they’re going to pollute,” says Jan Morrill, who studies mining at the environmental group Earthworks, which recently found that 76% of mining companies in the U.S. polluted groundwater after saying they wouldn’t.

One of the most problematic parts of mines is the tailings, or waste, Morrill says: Companies extract the minerals they need, then are left with a giant pile of rock, liquid, and chemicals that they store in ponds or behind dams that sometimes prove unstable. These tailings have caused landslides, excessive dust, and water pollution; more than 300 mine tailing dams have failed worldwide over the last century, according to Christopher Sergeant, a research scientist at the University of Montana.

It is not uncommon for tailings to leak into water, in fact, there is a permit that mine owners can get in case they find their projections were wrong and they need to discharge into U.S. waters.

Even “modern mines” that adhere to the latest U.S. standards—which are among the strictest in the world—still pollute, Earthworks has found. Though there are, theoretically, non-polluting ways to store mine tailings, doing so is much more expensive and mine operators have largely not paid to do so, Morrill says. That’s because, says Aimee Boulanger, executive director of the Initiative for Responsible Mining Assurance, “laws and markets have not fully incentivized companies to do that.”

Indeed, the Biden initiative to increase domestic mining includes, for example, a $700 million loan for Ioneer, a company planning a lithium mine on Rhyolite Ridge in Nevada, where environmental groups say the mine, as proposed, would cause the extinction of an endangered species called Tiehm’s buckwheat. The Administration is also spending $115 million to help Talon Nickel build a battery minerals processing facility in North Dakota, but the potential mine they would source from, in Minnesota, is opposed by Indigenous groups and environmentalists who fear it could contaminate wells in the area.

Still, the U.S. has a more rigorous regulatory environment than many other countries, she says, and there are domestic mines that even some environmentalists support, like the Stillwater Mine in Montana. Community organizations there signed a Good Neighbor Agreement in 2000 with the Sibanye-Stillwater Mining Company allowing the firm to extract platinum and palladium—while also establishing clear and enforceable water standards, restrictions to minimize local traffic, and third-party auditors to ensure the mine adheres to the standards it set out. The mine is now one of the top employers and private-sector income generators in Montana.

But advocates had to force the Agreement; three grassroots organizations sued to stop the construction of the mine, and after a year of negotiations, the mining company and grassroots groups agreed to the contract instead of going to court. With support from elected officials trying to find ways to mine more critical minerals in the U.S., companies may not feel the need to make similar promises to the local community.

The Freemans say their mine would not pollute the surrounding land and water, as the chemical composition of the crystals and the rocks around them is such that they would not dissolve into dangerous acid when exposed to air and water. Geologists that TIME/Maine Monitor spoke with agree with that assessment. Further, the crystals, says Mary, would be shipped out of state in large chunks for processing, so there would be no chemical ponds or tailings.

Many geologists agree that the Freemans’ proposal would not be as disruptive as other proposed mines across the country. Other metals (like nickel, silver, and zinc) typically occur in bands of rock deep below the surface that contain iron sulfides, which create sulfuric acid when exposed to air and water, polluting waterways for decades, a phenomenon known as acid mine drainage. Some spodumene crystals at Plumbago North, by contrast, have been naturally exposed to air and water for hundreds of millions of years and not broken down.

On a visit to the test quarry this spring, Gary Freeman pointed out one large piece of spodumene lying at the bottom of a nearby brook, the water over it rushing fast and clear, not the rusty orange of an acid-contaminated stream. (The waterway is known, fittingly, as Spodumene Brook.) “The water is so good Poland Spring wants to bottle it and sell it,” says Mary.

Still, Morrill, of Earthworks, says there’s just not enough research about the effects of hard rock spodumene mining to say for sure that the mine wouldn’t harm the environment. Since so many people in Maine depend on recreation and tourism for their livelihoods, she says, it makes the most sense to keep protective regulations in place.

Maine’s Department of Environmental Protection has rejected the Freemans’ request to consider the land a quarry, and is instead classifying spodumene as a metallic mineral. As the law stands, the Freemans will have to apply for permits under Maine’s 2017 Metallic Mineral Mining Act, a costly process (the application processing fee alone is $500,000) that would take years.

Meanwhile, the local community is divided. After all, in Maine it’s not difficult to find people still living with the long-term damage of older mines. On the other hand, many Mainers are pragmatic and understand the state has long, dark winters, and will need battery storage for any renewable energy it generates on sunny or windy days. The alternative is to continue relying on fossil fuels, which would exacerbate climate change.

Myles Felch, curator at the Maine Mineral and Gem Museum, is one of these practical Mainers. He was raised in Union, where a groundswell of opposition has formed to resist a proposal by Canada-based Exiro Minerals to look for nickel near a beloved local pond. Felch isn’t thrilled with the prospect, but also knows we can’t continue to be so detached from the minerals we use in our daily life.

“I love the place where I grew up and I wouldn’t want anything to ever happen to it,” says Felch. But “you need mineral resources. Most people were probably texting ‘stop the mine’ with a nickel cobalt battery in their phones.”