Cobalt-rich ferromanganese crust and nodule ores from seamount areas contain volcanic and sedimentary rocks as substrate or nuclei. During mining operations, these rocks should be separated as unfavorable waste rocks with the ferromanganese minerals. The cobalt-rich ferromanganese crust and nodule ores require mineral processing to remove the substrate/nuclei rock before the smelting. Deep-sea manganese nodule ores in contrast contain vanishingly small rocks, and can be directly treated with a metallurgical process without mineral processing treatment. This study is a physical and chemical description of the ores for the purpose of mineral processing, and reports estimates of the degree of liberation in a coarse crushed product of ores and its gravity separation results. From the obtained results a process flow-sheet for the beneficiation of cobalt-rich ferromanganese crust and nodules is proposed. (c) 2008 Elsevier B.V. All rights reserved.