Occurrence and Associations
Although todorokite is a common product of oxidation and leaching of primary manganese carbonate and silicate minerals, its major occurrence is in deep-sea ferromanganese nodules. Todorokite has been synthesised from birnessite in the laboratory, and it is possible that most natural todorokite is derived from birnessite. At the type locality in Akaigawa, Hokkaido, Japan, todorokite occurs as an alteration product of inesite (Ca2Mn2+7Si10O28(OH)2ยท5H2O) and rhodochrosite MnCO3). It is found as very fine fibrous flakes about 0.05 mm in length, loosely aggregated in sponge-like masses in druses in gold-bearing quartz veins. The original sample was rather impure since it contained a total of 2.43% insoluble phosphorus salts (P2O5SO3) and silica (SiO2).
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