Todorokite
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Todorokite is a rare complex hydrous manganese oxide mineral with formula: (Mn,Mg,Ca,Ba,K,Na)2Mn3O12·3H2O. It is a brown to black monoclinic mineral which occurs in massive or tuberose forms. It is quite soft with a Mohs hardness of 1.5 and a specific gravity of 3.49 - 3.82.
It was discovered in 1934 in the Todoroki mine, Hokkaidō, Japan. It is a component of deep ocean basin manganese nodules.
