Manganese nodule deposits exhibit variabity in distribution, deposit density, nodule morphology, and chemistry on scales of meters to thousands of kilometers. The Challenger Expedition recognized sufficient variation in nodule form to permit identification of a station location by inspection of a specimen nodule. The existence of a copper/nickel-rich nodule belt north of the equator in the Pacific was recognized in the 1950s and its character emphasized by early work of the IDOE Manganese Nodule Project. Through field work by the IDOE Project and by research programs in Germany and France, it has been posible to examine the detail of variability within well-defined regional patterns. Data from four small areas studied by the R/V Kana Keoki , R/V Moana Wave , and the F/S Valdivia , plus regional data within the Pacific equatorial nodule belt, show that the deposit variability is as high on a local as on a regional scale. An area 20 x 20 nautical miles, within the abyssal hill region of the northern Central Pacific, has been sampled intensively by R/V Valdivia during the VA-13/2 campaign. Selected manganese nodules retrieved either from free fall or box grabs were later analysed in laboratory using atomic absorption spectroscopy (AAS). It is likely that the samples were dried at 110°C for 24 hours and then ground for analytical purposes.

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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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.