How might a manganese nodule form?

Manganese nodules are formed at the bottom of the ocean when the metallic minerals settle down on the ocean floor.

Explanation:

The ocean floor-bed is covered with metal-bearing nodules. They spread throughout thousands of sq kilometers. Manganese nodules are one of the two forms of Manganese concentrations. The other one being Ferromanganese crusts.

Metals such as iron and manganese are present in sea-water in a concentrated form. A tiny nucleus is surrounded by chemical elements which makes it the catalyst to allow the accumulation of metallic compounds. Different metals precipitate in a concentrated form until a nodule reaches a fistful size.

Manganese nodules are formed in areas that have stable environmental conditions. This nods towards their slow growth. There are three processes by which the nodules are formed:

Hydrogenous Process Diagenetic Processes Mixed Process