Manganese nodules and crusts were sampled from box cores collected at the Manganese Nodule Program (MANOP) site H in the Eastern Equatorial Pacific ocean. For majority of site H nodule bottoms have smooth, lustrous patches, whereas nodule tops are generally rough and dull. The top/bottom orientation of each manganese nodule was labeled during curation. Most of the nodutes studied were cut in haIf, and a 3-5 mm layer was scraped from nodule tops and bottoms. The chemical analysis was performed on both top and bottom sides as well as on the whole specimen. Atomic absorption spectrometry (AAS) was used folIowing complete dissolution with HF and aqua regia in teflon bombs
