Manganese nodules have been found in huge abundance on the seabed around the Cook Islands. ‘Manganese Nodules in the Cook Islands’ is a book by Stuart Kingan that details the research on this resources.
Manganese nodules are concretions of many metallic oxides that grow on the deep ocean floor. The genetic process is not fully understood but it is partly chemical with a biological component. The nodules have built up very slowly. In the centre is a small piece of rock or a shark’s tooth. Around this the nodules have grown in layers with a cross section like that of a pearl.
Nodules have absorbed many of the elements present in seawater and contain over 70 elements including practically all metals. Growth has been very slow (in the order of about 2mm each million years). Deep-sea mining is attracting new interest with many new technological advances making the mining and processing of nodules much more practical and economically attractive.
Unlike other nodule deposits, Cook Islands nodules have high cobalt content. In the Cook Islands EEZ they are conveniently sitting on top of the sediment and in many places are on large plains on the sea floor.