Japan Identifies Large Share Of Heavy Rare Earths In Deep-Sea Mud Amid China Export Curbs

Japan has identified a high share of medium and heavy rare earth elements in deep-sea mud collected near the remote Pacific island of Minamitori, as it works to secure domestic supplies of critical minerals following tighter Chinese export controls.

An analysis of rare earth-rich mud recovered from the deep seabed earlier this year found that medium and heavy rare earth elements made up about 54% of the total rare earth content, Japan’s government said on Friday.

The government did not reveal the size of the deposits or the total amount of rare earths, saying the available data was limited because sampling was carried out over a short period and in a small area.

The findings come after Japan’s scientific drilling vessel Chikyu completed a month-long mission in February near Minamitori Island, about 1,900 km (1,200 miles) southeast of Tokyo.

The expedition marked the world’s first successful continuous retrieval of rare-earth-bearing seabed mud from depths of around 6 km (4 miles).

The project is part of Japan’s efforts to diversify supplies of critical minerals as China tightens export controls on heavy rare earths and related magnets, which are widely used in the defence and automotive industries.

About 50 metric tons of seabed mud were recovered during the mission.

According to the Cabinet Office’s national platform for innovative ocean development, the samples contained yttrium, which is used in aerospace, energy and semiconductor applications; gadolinium, which is used in magnetic resonance imaging and other high-tech applications; and dysprosium, which is used in high-performance magnets for electric vehicles.

Japan plans to begin a month-long large-scale mining trial in the same waters in February 2027, with a target of dredging 350 metric tons of mud per day.

The recovered material will be dewatered at Minamitori Island before being transported to the mainland, where it will be used to test separation, refining and smelting technologies.

The trial is expected to determine whether domestic production of rare earth elements is commercially feasible. A full assessment of industrialisation prospects is due by March 2028, said Kazushige Kikuchi, project manager at the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), which operates the Chikyu.

China imposed export controls on some heavy rare earths and related magnets in April 2025. It tightened restrictions on exports to Japan in January and twice again the following month, targeting major conglomerates.

Japan has not yet estimated the size of the rare earth deposits near Minamitori Island, saying further exploration and the planned mining trial will provide more data on their potential.

References: Reuters, OceanCrew