The risks of shortages for some crucial metals and uncertainty about the land-based reserves of several others justify the search to diversify our sources of supply and investigate their potential. Mineral resources in the deep sea are attracting increasing interest with the progressive discovery of various forms of ores. France possesses large areas of deep seafloor in the three oceans as well as world-class human and technological resources and know-how, resulting from over 40 years of experience. This study takes stock of knowledge about mineralisations and associated metals, technologies...