A South Korean mine has reopened after two decades of disuse, with the potential to be a reliable source of a rare metal critical for modern militaries that China has a near-stranglehold over.

Packing a high energy density and nearly as hard as a diamond, tungsten penetrates targets more effectively than other metals, making it essential for weapons like armor-piercing rounds.

Thanks to its durability, corrosion resistance and high conductivity, tungsten also has a wide range of civilian applications, from industrial cutting tools and light bulbs to electric vehicle batteries and microchips produced by businesses like Taiwan Semiconductor Manufacturing Company and Nvidia.

This has major implications for Washington’s push to diversify critical supply chains away from countries it considers adversarial.

Most of the U.S.’s imports of critical materials, such as tungsten, tantalum and rare earth elements (REEs), are either unavailable or produced in insufficient quantities domestically to ensure self-sufficiency, creating a “high potential for harm to national security in the event of a supply chain disruption,” the non-partisan Government Accountability Office wrote in a September report.

Sourcing them from South Korea, a longtime U.S. security ally, is “vital for national security,” Gracelin Baskaran, director of the Critical Minerals Security Program at the Center for Strategic and International Studies (CSIS), told Newsweek.

Concerns over China’s near-monopoly on REEs and other critical minerals have grown since former President Donald Trump launched a trade war with the world’s second-largest economy.

These concerns were compounded by supply chain disruptions during the COVID-19 pandemic and China’s demonstrated willingness to use its dominance over these resources as leverage, such as its temporary REE embargo against Japan in 2010 after a Chinese fishing boat collided with Japanese coast guard vessels, sparking a diplomatic incident.

Under President Joe Biden, the U.S. administration has continued addressing these vulnerabilities. In September, the Biden administration imposed a 25 percent tariff on tungsten and other critical minerals as part of a broader strategy to protect U.S. industries and reduce reliance on Chinese-controlled supply chains.

“Economic analyses… generally find that the Section 301 tariffs have contributed to reducing U.S. imports of goods from China and increasing imports from alternate sources, including U.S. allies and partners, thereby potentially supporting U.S. supply chain diversification and resilience,” the Office of the U.S. Trade Representative said in a press release.

Washington is not alone. Last year, the Council of the European Union announced a 33-percent anti-dumping duty on tungsten imports from China.

Enter Sangdong, a sleepy town 115 miles southeast of Seoul in South Korea‘s Gangwon Province. Once a major source of South Korea’s income, Sangdong’s mine shuttered in 1994 as China ramped up tungsten production at a lower cost.

Believed to be one of the largest tungsten sources globally, with 8.7 million tons of proven and probable reserves, Sangdong could reestablish South Korean tungsten on the world stage and serve as a prime example of U.S. “friend-shoring” of essential resources.

Canadian firm Almonty Industries acquired the rights to the mine in 2015. Its subsidiary, Almonty Korea Tungsten Corp., reopened operations last month in Gangwon Province.

“Almonty has a rare and unique opportunity at Sangdong, because of the formation of the deposit, to roughly double production capacity from approximately 640 kilotons to 1.2 million tons within two to three years after we start production,” Almonty Industries CEO Lewis Black told Newsweek.

With the inclusion of Sangdong’s output, Almonty aims to supply 43 percent of tungsten produced outside China and 12 percent of global supply by 2027. Ultimately, the Sangdong mine could be capable of supplying half of the world’s non-Chinese tungsten, Black said.

“Probably the best indication of demand is when customers willingly pay extra,” Black said regarding trends in sourcing tungsten from non-Chinese suppliers. Almonty’s tungsten from its Panasqueira mine in Portugal alone is selling at a 15 percent premium, he noted, citing the tightening supply from “transparent sources.”

As for Sangdong, the company has secured an “unprecedented” floor price of $235 per metric ton unit.

Black said the U.S. government is “very aware” of Almonty’s operations, particularly at Sangdong, with a United States Geological Survey delegation visiting the site earlier this year. “We’re told USGS will make a ‘significant update’ on its assessment of the mine in its 2025 report. Sangdong will be a big change in the global tungsten supply chain,” he said.

“Sangdong provides an alternate source of tungsten supply, which can help reduce the American reliance on Chinese and Russian tungsten,” Baskaran said.

She predicted the U.S. would commit more funding to develop domestic tungsten mining and processing capabilities through the Defense Production Act, a 1950 law that empowers the government to prioritize and fund essential materials for national defense.

Newsweek reached out to the U.S. Department of Defense with a written request for comment.