Cobalt-rich ferromanganese crusts from the seafloor are gaining significance due to the presence of a variety of major, minor, and trace metals that are of strategic importance for sustained demands of the industry in future. This chapter describes the occurrence and nature, mineralogy, formation and growth, chemical composition as well as their inter-relationships. The chapter further looks at total and regional metal potentials and proposes a resource assessment model for ferromanganese crust deposits and their economic considerations.