Annotated record of the detailed examination of manganese nodules from around the world oceans

Manganese nodules collected off Baja California have layers (zones) which are texturally and compositionally distinct. Massive and mottled zones consist mostly of cryptocrystalline todorokite and birnessite containing relatively high concentrations of Mn, Ni and Cu. Compact, columnar and laminated zones consist mostly of more iron- rich opaque amorphous material. Within these two groups the individual zones can be distinguished in part by their clay content. These results indicate that systematic research on nodule chemistry, mineralogy, growth rates and beneficiation should include careful analysis of individual layers within the nodules.