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.

From 1983 until 1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions. At the time it was the most extended data compilation on ferromanganese deposits world wide. Initially published in a proprietary format incompatible with present day standards it was jointly decided by AWI and NOAA to transcribe this legacy data into PANGAEA. This transfer is augmented by a careful checking of the original sources when available and the encoding of ancillary information (sample description, method of analysis...) not present in the NOAA-MMS database.

Supplement to: Sorem, Ronald K; Foster, Allan R (1972): Marine manganese nodules: importance of structural analysis. in: Proceedings of the the 24th International Geological Congress, Montreal, 192-200