Geochemistry of Manganese and Manganese Nodules in the Ocean

Manganese nodules were first discovered on the ocean floor 160 miles south-west of the Canary Islands on February 18, 1803, during the first complex oceano­ logical cruise of the Challenger. They surprised researchers by their unusual shape and also by their unusual chemical composition; nevertheless for many years after­ wards, they were considered merely as one of Nature''s exotic marine tricks....