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Polymetallic nodules, also called manganese nodules, are mineral concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. As nodules can be found in vast quantities, and contain valuable metals, deposits have been identified as a potential economic interest. [ 1 ]
The CCZ is regularly considered for deep-sea mining due to the abundant presence of manganese nodules. The CCZ extends around 4,500 miles (7,240 km) East to West [4] and spans approximately 4,500,000 square kilometres (1,700,000 sq mi). [5] The fractures themselves are unusually mountainous topographical features.
Polymetallic nodules on the deep seabed in the CCZ Example of manganese nodule that can be found on the sea floor. Polymetallic nodules are found at depths of 4–6 km (2.5–3.7 mi) in all major oceans, but also in shallow waters like the Baltic Sea and in freshwater lakes. [23] [24] They are the most readily minable type of deep sea ore. [25]
Nodule is also used for widely scattered concretionary lumps of manganese, cobalt, iron, and nickel found on the floors of the world's oceans. This is especially true of manganese nodules. Manganese and phosphorite nodules form on the seafloor and are syndepositional in origin. Thus, technically speaking, they are concretions instead of nodules ...
The nodules form in a manner similar to pearls; there is a central object around which concentric layers are slowly deposited, causing the nodule to grow over time. The composition of the nodules can vary somewhat depending on their location and the conditions of their formation, but they are usually dominated by manganese- and iron oxides.
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Manganese is a silvery-gray metal that resembles iron. It is hard and very brittle, difficult to fuse, but easy to oxidize. [11] Manganese and its common ions are paramagnetic. [12] Manganese tarnishes slowly in air and oxidizes ("rusts") like iron in water containing dissolved oxygen. [13]
Todorokite is a rare constituent of the manganese oxide deposits at Saude and Urandi, in Bahia, Brazil, as a result of supergene enrichment of the metamorphic country rock that contains spessartine (Mn 2+ 3 Al 2 (SiO 4) 3) and other manganese minerals.