Polymetallic Crust

A polymetallic crust, or cobalt-rich ferromanganese crust, is a hard pavement of manganese and iron oxides that precipitates from seawater onto the bare rock flanks and summits of seamounts and ridges, growing at depths of roughly 400 to 7,000 meters over millions of years. The crusts concentrate cobalt along with nickel, manganese, and traces of rare metals, which makes them one of the three deep-sea mineral resource types the International Seabed Authority regulates. Unlike loose nodules on flat abyssal plains, crusts are bonded to steep, biologically rich seamount substrate, so recovery is harder and the habitat impact more acute. The ISA has granted crust exploration contracts in the western Pacific. Exploitation rules remain under negotiation in the Mining Code.