Manganese nodule

Polymetallic nodules, also called manganese nodules, are rock concretions on the sea bottom formed of concentric layers of iron and manganese hydroxides around a core. The core may be microscopically small and is sometimes completely transformed into manganese minerals by crystallization. When visible to the naked eye, it can be a small test (shell) of a microfossil (radiolarian or foraminifer), a phosphatized shark tooth, basalt debris or even fragments of earlier nodules.

Related Topics:
Sea - Iron - Manganese - Hydroxide - Crystallization - Radiolarian - Foraminifer - Shark - Basalt

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Nodules vary in size from tiny particles visible only under a microscope to large pellets more than 20 centimeters across. However, most nodules are between 5 and 10 cm in diameter, about the size of potatoes. Their surface is generally smooth, sometimes rough, mammilated (knobby) or otherwise irregular. The bottom, buried in sediment, is generally rougher than the top.

Related Topics:
Microscope - Centimeter

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