| Global marine nonfuel minerals can be classified into five major groups: (1) commodities recovered directly from seawater; (2) placers and aggregates; (3) the agricultural commodities, including phosphorites, glauconites, potash and sulfur; (4) ferromanganese deposits; and (5) polymetallic sulfide deposits. With the exception of the agricultural commodities, other marine mineral deposits are grouped on the basis of a common depositional and genetic environment.;The economic potential and ultimate viability of marine minerals is determined by the same factors that influence the viability of land-based deposits. Grade, geometry and magnitude of the deposit, proximity to markets and infrastructure, price, capital and operating costs, and competition from other producers are the dominant factors. Further, the availability of technology and the rate of technological change, as determined by increased scientific understanding and improved recovery performance, influence the time-frame over which marine minerals production may become a more significant source of raw materials. The broader issues of prevailing geopolitical realities, such as security of tenure, financial risk, strategic interests, public policy and international law, also influence the long-term prospects for marine minerals development, particularly in the deepsea.;Actual minerals production from marine sources in recent years has declined in real economic terms in response to excess land-based capacity, depressed metals prices, and unfavorable technical, economic, legal/political factors. Unlike the 1960s and 1970s, when much of the emphasis was directed at exploring and developing technology to exploit deepsea manganese nodules, recent developments are directed at nearshore or continental shelf deposits. Much of the deepsea research has shifted from nodules to ferromanganese crust and polymetallic sulfide deposits. This research appears motivated more by the need to increase scientific understanding of ore genesis and long-term strategic minerals development, than by near-term commercial factors.;For the remainder of the current century, the most promising marine mineral targets are likely to be those that have a demonstrated production history, or that occur in the nearshore setting (with the exception of the Red Sea metalliferous brines), where existing mining and processing technology allow for competitive recovery. Examples include offshore noble metal placers, 'light' heavy mineral beach placers and offshore sand and gravel deposits near major metropolitan markets. |
