1. Manganese nodules are metal-rich stones that grow about 10 millimeters in a million years
The stones are called manganese nodules (or polymetallic nodules). A nodule starts around a small core, such as a bit of rock, and layers of iron and manganese minerals slowly build up around it. A sample of nodules from the Clarion-Clipperton Zone, a huge stretch of Pacific seabed between Hawaii and Mexico, was about 28 percent manganese, with smaller shares of iron, nickel (1.3 percent), copper (1 percent) and cobalt (0.2 percent)[1]. Those last three metals are the ones that make nodules interesting to mining companies.
Nodules lie on abyssal plains, usually 3,000 to 6,000 meters deep. On the seabed surface they are reported to grow about 10 millimeters per million years, a bit faster, 10 to 100 millimeters, when they are buried in sediment[1]. Measure 1 centimeter on a ruler: that is roughly a million years of growth. The numbers are approximate and vary from place to place.
That slowness changes the question. A forest regrows after logging. A nodule field will not regrow on any timescale people care about, so whatever is taken away stays gone.
2. A Japanese survey estimated about 230 million tons of nodules near a remote island
Japan is short of many metals, so it has searched its own waters. Minamitorishima is a tiny island about 2,000 kilometers southeast of Tokyo. Under the law of the sea, a country has an exclusive economic zone (EEZ) reaching up to 200 nautical miles from its coast, where it holds sovereign rights over the natural resources, including those of the seabed. Minamitorishima lies inside Japan's EEZ.
In June 2024 the Nippon Foundation and a research team from the University of Tokyo said they had found a dense field of nodules there: about 230 million tons, spread over roughly 10,000 square kilometers at depths of 5,200 to 5,700 meters. They estimated about 610,000 tons of cobalt and 740,000 tons of nickel inside, which they compared with Japan's consumption: more than 75 years of cobalt and more than 11 years of nickel[2].
Be careful with those "years" figures. They compare an estimate with how much Japan uses; they do not say it can all be taken out, or at what cost. The foundation's own numbers are an announcement by a group that supports ocean research, and some news reports repeated them with small errors, so the safest reading is "a large estimated resource that still has to be proved."
3. In 2026 a Japanese ship lifted rare-earth mud from nearly 6,000 meters, which proved the lifting can be done
Nodules are not the only treasure. The seabed near Minamitorishima also holds mud rich in rare earth elements, metals used in strong magnets for electric motors and wind turbines. China is a major source of heavy rare earths, which is one reason Japan wants a source of its own.
Japan's deep-sea drilling ship Chikyu lowered a long pipe to the seabed and brought up the first batch of mud on February 1, 2026. The government announced it the next day, at a depth of nearly 6,000 meters, and called it a world first for rare-earth mud from that depth[3]. Six thousand meters is more than 1.5 times the height of Mount Fuji.
What did this prove, and what did it not? It proved that a pipe can lift mud from that depth. Officials said the amount of rare earth in the mud still had to be analyzed and that the full chain, from mining to separating and refining the metals, still had to show it can make money[3]. One test run is a first step, not a mine.
4. Nodule fields are full of animals, and many of them have never been named
It is easy to imagine the deep seabed as an empty desert. Studies in the Clarion-Clipperton Zone say otherwise. A team led by Muriel Rabone of the Natural History Museum in London combined many earlier records and reported in 2023 that, according to news reports of the study, about 5,500 animal species had been recorded there, and that an estimated 88 to 92 percent of them had no scientific name yet. The authors note that counting the same animal under different names probably makes the total a little too high[4].
Why does this matter for mining? Because the stones are homes. In a 2016 study, Diva Amon of the University of Hawaii and colleagues found that most of the large animals they saw seemed to depend on the nodules themselves, and that more animals lived where nodules were more common[5]. Nodule mining machines would take away exactly those stones.
One caution: this work was done in the Pacific zone between Hawaii and Mexico, not near Minamitorishima. It shows what scientists should check before mining anywhere, not what lives in Japan's own area.
5. A 2024 study suggested nodules may produce oxygen in the dark, but experts say it is still an open question
There is another reason to be careful. In 2024 a team led by Andrew Sweetman of the Scottish Association for Marine Science reported that, in experiments on the nodule-covered seabed of the Pacific, oxygen rose to more than three times the background level over two days. Plants cannot make oxygen without light, so the authors suggested that voltages of up to 0.95 volts on nodule surfaces might split seawater into hydrogen and oxygen[6].
This is a hypothesis, and it is disputed. The International Seabed Authority (the body you will meet in the next section) says that whether nodules produce "dark oxygen" remains an open question, with scientists holding different views and more research under way[7]. Even so, the idea shows how much about these stones is unknown, and why some scientists want more answers before any digging.
6. The International Seabed Authority decides the rules for the seabed no country owns, and its mining code is not finished
Most of the deep seabed lies outside every country's waters. Under the UN Convention on the Law of the Sea, this region, called "the Area", covers around 54 percent of the world's oceans, and its minerals are treated as the common heritage of humankind, to be managed for the benefit of present and future generations. The International Seabed Authority (ISA), set up in 1994 and based in Jamaica, organizes and controls mineral activities there. It has 172 members: 171 states plus the European Union[7].
So far the ISA has approved no commercial mining. It has issued exploration contracts only, to 21 contractors in 31 areas, together about 1.445 million square kilometers or 0.7 percent of the Area[7]. Rules for actual mining, called the Mining Code, are still being negotiated. In March 2026 the ISA Council discussed 29 of the 32 remaining issues and agreed in principle on a Compliance Committee and an equalization mechanism. The ISA states that regulations must be agreed before any exploitation can begin[7][8]. This describes the situation in March 2026; later meetings may have changed it.
Not everyone is waiting. The ISA's media Q&A discusses an executive order from the United States and a company's plan to seek a U.S. license for seabed mining outside the ISA process, and says that commercial mining in the Area without its authorization would violate international law[7]. That is the ISA's own position, and the dispute is ongoing.
Japan's test is a different case. Minamitorishima lies inside Japan's own EEZ, so the ISA does not govern it. Japan's test and the world's rule-making are two sides of one question: when, and under what conditions, is it right to take things from a place that heals this slowly?
How to explore deep-sea mining for yourself
- Feel a million years. Hold a ruler and look at 1 centimeter (about 0.4 inch). That is about how much a nodule on the seabed surface grows in a million years. What would you want to know before taking one?
- Find the places on a globe. Locate Hawaii, Mexico and Minamitorishima. The Clarion-Clipperton Zone lies between the first two; Japan's test happened in the far northwest Pacific. How far apart are they?
- Read the original. The ISA's Q&A for media is written for general readers, and the GeoExPro article "Deep-Sea Potato Fields" has the nodule growth and composition figures.