The Bureau of Mines performed an "economic reconnaissance" of mineral resources on the outer continental shelf in response to proposals by the Department of the Interior's Minerals Management Service to offer offshore mineral leases. Three marine placer areas with near-term potential for containing economically viable deposits are: (1) gold-bearing placers near Nome, Alaska; (2) chromite-rich black sands offshore southern Oregon; and (3) titanium-bearing sands on the Atlantic shelf off Virginia and Georgia. Available resources information was used to construct deposit models that allowed evaluation of engineering parameters and costs associated with potential mining and processing operations. Economic sensitivity analyses were performed on slected parameters to establish threshold conditions of economic viability. Estimated conditions for viable operations are distinctly different for the three resource areas. A dredging operation off Nome, Alaska, is expected to be profitable at present gold prices. Mining operations offshore southern Oregon could be viable for deposits of at least 50 million short tons (mst) that contain recoverable grades of 6.3 pct cr203, 1.0 pct ti02 (in ilmenite), 0.2 pct rutile, 0.7 pct zr02, and 0.005 Tr oz/st gold. A mining operation on the Atlantic shelf could be economically viable if large deposits are discovered that contain concentrations of heavy minerals of about 4.2 pct total recoverable oxides consisting of 3.6 pct tio2 in ilmenite, rutile, and leucoxene, 0.4 pct zro2, and 0.2 pct total rare earth oxides in monazite.