Prospecting and exploration for manganese nodules has as its ultimate objective the discovery and delineation of an area of the ocean floor with reserves of sufficient quantity and quality to support a mining operation under existing economic technical and political conditions. While prospecting concentrates primari- lyon the collection of geological information an exploration programme includes other activities that relate to the develop- ment of technology financial analysis of the prospect and environmental protection. Such work on a deposit in turn leads to the development of a mine-site. The mine-site concept brings together information in a way that recognizes the interplay among a number of dynamic factors which must satisfy a set of technical and economic conditions. Defining a mine-site therefore is a process of accounting for those factors. Throughout the years of meetings of the Third United Nations Conference on the Law of the Sea many questions arose about ocean mine-sites. Two related topics in particular received attention: the total number of available mine-sites and the amount of area necessary for a mining operation. Both of these topics have been subject to a great deal of speculation and even with the best available information there remains a degree of uncertainty that arises from both incomplete knowledge and natural variability in the seabed and the resource and different technology and production objectives. For example estimates of the size of the area necessary for an ocean mine-site vary even when made by the same company.