Japan said Friday that medium and heavy rare earth elements made up about 54% of the rare earth content in deep-sea mud recovered near a remote Pacific island, supporting the country's efforts to secure domestic sources of critical minerals as China tightens export controls.

The government-backed mining vessel Chikyu collected about 50 tonnes of mud during a month-long mission that was completed in February near Minamitori Island, roughly 1,900 km southeast of Tokyo. Minamitori Island, also known as Marcus Island, lies within Japan's exclusive economic zone, giving Tokyo sole jurisdiction over resource development in the surrounding waters.

The expedition was described as the world's first successful continuous recovery of rare earth-bearing seabed mud from a depth of about 6 km. Heavy and medium rare earths — the category that dominates this deposit — are generally scarcer and more economically valuable than light rare earths because they are essential to high-performance magnets, defence technologies, and advanced electronics, and are difficult to substitute.

"The trial is expected to verify the feasibility of domestic rare earth production," Kazushige Kikuchi, project manager at the Japan Agency for Marine-Earth Science and Technology, told Reuters. A full assessment of the project's commercial potential is expected by March 2028.

Reducing reliance on China

The project could help Japan cut its dependence on China for strategic minerals used in defence equipment, electric vehicles and advanced technologies. China accounts for the dominant share of global rare earth mining and an even larger share of refining capacity, giving Beijing significant leverage over downstream supply chains. Japan's push for alternative sources has taken on greater urgency before: in 2010, a diplomatic dispute between Tokyo and Beijing led to a temporary suspension of Chinese rare earth exports to Japan, underscoring the vulnerability of industrial economies to supply interruptions.

Beijing imposed export controls on some heavy rare earths and related magnets in April 2025, then tightened restrictions on shipments to Japan in January and twice more the following month.

Japan's government did not disclose the overall size of the rare earth deposit or the concentration of material in the recovered mud. Officials said the sampling program's limited duration and geographic scope did not provide enough data for a broader resource estimate.

The analysis identified yttrium, which is used in aerospace, energy and semiconductor applications; gadolinium, used in magnetic resonance imaging and other high-tech products; and dysprosium, a key component in high-performance magnets for electric vehicles.

Japan has also been examining rare-earth mining from deep seabed mud as part of broader efforts to assess offshore mineral resources.

In 2024, researchers from the University of Tokyo and the Nippon Foundation identified more than 200 million tonnes of manganese nodules rich in battery metals in the Pacific Ocean, pointing to significant resource potential at depths of around 5,500 meters.

A separate survey by the University of Tokyo and the Nippon Foundation estimated that the seabed nodules contain about 610,000 tonnes of cobalt, enough for 75 years of Japan's consumption, and 740,000 tonnes of nickel, covering 11 years of domestic demand.

Commercial testing planned

Japan plans to conduct another month-long mining trial in the same waters beginning in February 2027, with a target production rate of 350 tonnes of mud per day.

The material will be dewatered on Minamitori Island, about 1,900 km southeast of Tokyo, before being shipped to Japan's mainland for separation, refining and smelting tests.

The pilot program is intended to determine whether the offshore resource can support commercial rare earth production and help reduce Japan's reliance on imported supplies. Deep-sea mining projects worldwide have drawn scrutiny from environmental groups and some governments over potential damage to seafloor ecosystems, and any large-scale operation would likely face similar questions about environmental impact and regulatory approval.