A Tremendous Supply of Rare Earth Metals Is Sitting in Japanese Waters

by Joel Hruska

Certain so-called “rare-earth” metals are vital to modern manufacturing and technology. Applications range from lasers and magnets to ceramic capacitors, oxidative agents, high-temperature superconductors, stainless steel, and PET scanners. A new report on the sea floor around Japan’s Minami-Tori-shima, also known as Marcus Island, indicates the mud is positively saturated with rare-earth elements and yttrium, abbreviated REY. (Yttrium is not always classified as a rare-earth element, but is extremely similar.)

Finding an area with a high concentration of rare-earth elements is, well, rare. The REY elements aren’t actually unusual on Earth; cerium is the 25th most abundant element within the Earth’s crust and is more prevalent than copper. While they may not be particularly hard to find in an absolute sense, they tend to be distributed over wide areas, as opposed to in concentrations that would make them easier to mine. There are 17 different rare-earth elements, and while the specifics of where they are mined varies somewhat depending on the element, most REY mining currently occurs in China, with Australia as the second-largest worldwide supplier.

In 2011, research reports indicated that REY-rich mud with mineral concentrations up to 2,230 ppm was widely distributed across the Pacific Ocean. A subsequent 2013 report focused on Marcus Island showed particularly rich deposits of up to 5,000 ppm REY existed around the small coral atoll. The richest samples were up to 0.66 percent rare earth oxides, compared with a typical concentration of 0.05 to 0.5 percent for Chinese mines.

This latest survey was a detailed examination of the REY deposits around Minami-Tori-shima to better gauge the total amount of potentially recoverable material. Here’s what they found:

The calculated ΣREY for the entire research area is more than 16 million tons of rare-earth oxides (Mt-REO) (average ΣREY=964 ppm). In addition, the mud is especially enriched in Y [yttrium] and HREE [heavy rare earth elements], which accounted for 44% (Y: 4.4 Mt-REO; HREE: 2.6 Mt-REO) of the total amount of REY in this region. The research area was estimated to be able to supply Y, Eu, Tb, and Dy for 780, 620, 420, and 730 years, respectively, and has the potential to supply these metals on a semi-infinite basis to the world.

The report has more good news in it. The grains of rare earth material recovered off the sea floor can be separated from the grains of unwanted material when filtered by size. Filtering the particles through a hydrocyclone further concentrated the final product to 260 percent of the base level found in the original sample.

Either or both of these techniques could be utilized in any commercial recovery effort, thereby reducing the amount of material that would need to be lifted off the ocean bottom in the first place or hauled back to port for processing. The more of the work that can be performed in situ, the more cost-efficient the mining process would be.

These reserves of rare earth materials could prove a potent long-term resource for Japan, and are an additional potential bulwark against any single nation dominating the rare earth market.

Originally published at www.extremetech.com on April 13, 2018.