Metallic nodules

Extracting mineral resources from the deep-sea environment has been studied since several decades. Among materials which could be mined, polymetallic nodules (also commonly called manganese nodules) are rock concretions on the sea floor. They were first discovered at the end of the 19th century in the Kara Sea, in the Arctic Ocean off Siberia, then in other oceans.

They are probably the most attractive mineral resources, with exploitable levels of metals such as nickel, copper and cobalt. There are four oceanic regions with the greatest commercial interest. The most promising is in the equatorial Pacific Ocean : the Clarion-Clipperton Zone with an area of around 9 million square kilometres, approximately the size of Europe.  On average, one square metre contains around 15 kilograms of manganese nodules. Especially rich areas can have up to 75 kilograms. The total mass of manganese nodules here is calculated to be around 21 billion tonnes.

They can be harvested without drilling and should have much less solid wastes than land-based mining. Profitable extraction of metallic nodules competes with established land-based mining activities. It faces technological challenges at below 4000 meters, and environmental challenges. The commercial exploitation of deep-sea minerals has still to be approved by the International Seabed Authority, a UN body.