Why do manganese spheres sometimes form in the ocean?

Manganese nodules discovered on the deep seafloor in January 2015. Credit: Thomas Walter. Manganese nodules have been found in every ocean, but are most common in the Pacific Ocean. read more

Simple (simplistic) answer: Manganese nodules precipitate when the concentration of Mn in the water is higher than the solubility. Just like sugar crystallizes out of water to make rock candy. Better answer: We don't know. read more

Manganese nodules have been found in every ocean, but are most common in the Pacific Ocean. The metal lumps, which most often look like pancakes, are formed of layer upon layer of metal ore that slowly crystallizes around a core. read more

Most manganese ores are from extensive layers of manganese-rich sedimentary rocks that formed in ancient oceans under specialized conditions. These occurred when changes in the oxidation state of ocean water first caused high concentrations of dissolved manganese and later precipitated various manganese minerals that became concentrated on the seabed. read more