If nodules were chemically homogeneous objects, their bulk compositions would paint a complete picture. But they are not, as can be assumed simply from visual recognition of their diverse structural elements. Successively finer sampling of individual nodules reveals an increasingly greater degree of inhomogeneity, the details of which are resolvable down to microprobe scale. For this study, the chemistry of the largest distinctly separable structural elements has been examined, in order to learn how much more information can be gained from such an approach than from whole-nodule analyses. Compositional data for selected nodule structure zones are presented in Appendix N. Concentrations were determined by atomic absorption spectrophotometry. The analysed part of the Mn nodule outer manganese rich rind or the outer part of the ferromanganese crust were dried at 110°C for about 48 hours, and ground to a fine powder.

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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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.This dataset represents the digitized version of Appendix N - pp. 308 of the related publication.