Japan Deep-Sea Rare Earth Mud Analysis Highlights Heavy Element Potential

Japan has identified a high proportion of medium and heavy rare earth elements in deep-sea mud collected from the Pacific Ocean, strengthening its efforts to secure alternative supplies of critical minerals. However, the government has not revealed the overall size of the deposits or the total rare earth content, stating that the available data remains insufficient because sampling covered only a limited area and took place over a short period.

Deep-Sea Analysis Reveals Significant Rare Earth Composition

According to the Japanese government, medium and heavy rare earth elements made up about 54% of the total rare earth content in the seabed mud recovered earlier this year. Even so, officials declined to estimate the scale of the resource. They explained that the current findings do not provide enough information to determine the full extent of the deposits because of the restricted duration and geographic scope of the sampling campaign.

Earlier this year, the Japanese scientific drilling vessel Chikyu completed a month-long mission near Minamitori Island, located about 1,900 km southeast of Tokyo. During the expedition, the vessel achieved the world’s first successful continuous recovery of rare-earth-bearing seabed mud from depths of around 6 km below the ocean surface.

Mission Supports Japan’s Critical Mineral Strategy

The project forms part of Japan’s broader strategy to diversify supplies of critical minerals. This effort has gained urgency as China has tightened export controls on heavy rare earth elements and related magnets. These materials play an essential role in the defence and automotive industries because they are used in a wide range of advanced technologies.

During the expedition, researchers recovered about 50 metric tons of seabed mud. Analysis of the material identified several valuable rare earth elements. These included yttrium, which supports aerospace, energy and semiconductor applications. The study also confirmed the presence of gadolinium, which is used in magnetic resonance imaging and other advanced technologies. In addition, the samples contained dysprosium, a key material used in high-performance magnets for electric vehicles.

The Cabinet Office’s national platform for innovative ocean development reported the findings following the analysis of the recovered material.

Large-Scale Mining Trial Planned for 2027

Japan now plans to expand the project with a month-long large-scale mining trial scheduled for February 2027 in the same waters. The trial aims to dredge approximately 350 tons of seabed mud each day.

After recovery, the mud will undergo dewatering at Minamitori Island before transport to the Japanese mainland. There, researchers will test separation, refining and smelting technologies to evaluate the practical processing of the material.

The trial will help determine whether domestic rare earth production can become commercially viable. Kazushige Kikuchi, project manager at the Japan Agency for Marine-Earth Science and Technology, which operates the Chikyu, said the programme is expected to assess the feasibility of industrial production. A comprehensive evaluation of industrialisation prospects is due by March 2028.

Meanwhile, the project continues against the backdrop of tighter Chinese export restrictions. Beijing imposed export controls on selected heavy rare earth elements and related magnets in April 2025. It then strengthened restrictions on exports to Japan in January and introduced two further rounds of tighter measures the following month, targeting major conglomerates.

With inputs from Reuters