Emery, K.O. and J.M. Broadus
Marine Mining, Vol. 8, pp. 109-121, 1989 WHOI-R-89-008
Marine mining has been conducted on local and generally small scales for thousands of years. Large-scale recovery from beaches and piers began only about 40 years ago, and soon afterward powered ships and tools and new exploration methods revealed the presence of economic concentrations of oil and gas, sand and gravel, and some heavy minerals beyond the beach. These materials are in relatively shallow waters of the continental shelf and now are known well enough to be considered reserve ores. Rapid success for them led to immediate expectation of marine mining of many other minerals that have higher value per unit weight, but they occur in deeper waters beyond the shelf where conditions are more difficult and costs are higher. They include phosphorite, ferromanganese nodules and crusts, and (less than a decade ago) polymetallic sulfides. All are still potential resources that cannot yet be considered reserve ores. Increased knowledge of the deep ocean floor and its natural processes is likely to be applied first to expanding the reserves of similar deposits now on land and perhaps later to ocean floor mining. Moreover, ocean floor mining must compete economically with improved methods of recovery from existing low-grade resources on land and from waste piles left from earlier and less efficient methods of mineral recovery.