Polymetallic nodules are a concept and a deep-sea mineral resource. They are potato-sized rock concretions found on the abyssal plains of the ocean floor, typically at depths of 4,000-6,000 meters. The nodules are primarily composed of manganese (around 29%) and iron hydroxides, but their economic value comes from critical metals like nickel (~1.4%), copper (~1.3%), and cobalt (~0.25%). These metals are vital for technologies such as electric vehicle batteries and renewable energy systems.
The nodules were first discovered in the Kara Sea in 1868, and the HMS Challenger expedition (1872–76) confirmed their widespread occurrence. Serious commercial interest was sparked by John L. Mero's book, The Mineral Resources of the Sea, in 1965. They form extremely slowly, growing at a rate of a few millimeters per million years, as metal oxides precipitate from seawater around a nucleus like a fossil or rock fragment.
The exploration and potential exploitation of these nodules are governed by the International Seabed Authority (ISA), which was established in 1994 under the UN Convention on the Law of the Sea (UNCLOS). India is a key player, having been the first country to receive the status of a Pioneer Investor in 1987, which allocated it an exclusive area in the Central Indian Ocean Basin (CIOB) for exploration. India's efforts are currently channeled through the Ministry of Earth Sciences' Deep Ocean Mission, which is developing deep-sea mining technology like the Varaha-3 machine.
Recently, the regulatory mechanism has seen changes, such as the US National Oceanic and Atmospheric Administration (NOAA) finalizing revisions on January 21, 2026, to its regulations under the Deep Seabed Hard Mineral Resources Act (DSHMRA). This revision replaced the sequential two-step process by allowing a consolidated application for both exploration licenses and commercial recovery permits to expedite the permitting timeline.