The metal content of selected manganese nodules from the Pacific and Southern oceans was determined as follows: boiling of a suspension of 100 mg sample in 25 ml of 4 M hydrochloride acid; filtering the acid leachate through 0.2 ~m membrane filters pre-rinsed with 4 N HC1; diluting the filtrate to 100 ml with distilled water; analysing the metal concentrations by atomic absorption spectrometry with standard solutions prepared in 1 M hydrochloride acid.

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1989 NOAA-NCEI compiled the NOAA-MMS Marine Minerals Geochemical Database from journal articles, technical reports and unpublished sources from other institutions.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