Todorokites: a new family of naturally occurring manganese oxides.

Todorokites are found in numerous terrestrial deposits and are important copper- and nickel-bearing materials in manganese nodules. Their structures are highly disordered, not well known, and controversial. High-resolution transmission electron microscopy reveals that terrestrial todorokites consist of tunnel structures of previously unreported dimensions and that these tunnel structures are intergrown coherently on a unit cell scale. Many types and degrees of disorder are evident in the high-resolution images. These newly discovered structures indicate a need for a revised nomenclature of tunnel manganese oxides, and such a system is suggested.