Beneficiation studies on cobalt-rich Mn crust from the Hawaiian Islands and Johnston Atoll exclusive economic zone (EEZ) have shown that magnetic separation and conventional and column froth flotation are promising techniques. Column flotation produces metallurgical results similar to those from conventional flotation but requires fewer processing stages. The best flotation collectors are mixtures of neutral oils (diesel fuel, kerosene) with fatty acids and minor amounts of sulfonate. Flotation in sea water of minus 28-mesh cobalt-rich manganese crust (with substrate) assaying 6.2% Mn, 0.20% CO, and 0.13% Ni, with a mixture of 2 kg/ton sulfonate, and 5 kg/ton each of diesel fuel and distilled oleic acid, or 7.5 Kg/ton each of diesel fuel and unitol CTF tall oil, has produced concentrates containing more than 15% Mn with 91.2- to 94.2-% Recovery. The concentrate also contained approximately 0.57% CO and 0.32% Ni with 93% CO recovery and more than 85% Ni recovery. The paramagnetic Mn- , CO-, and Ni-containing minerals can be separated from the nonmagnetic gangue by high-intensity magnetic separation. Magnetic separation testing of minus 35- plus 100-mesh (425- by 150-um) material, assaying 6.6% Mn, 0.24% CO, and 0.13% Ni, produced a concentrate assaying 15.6% Mn, 0.6% CO, and 0.26% Ni, which contained 82.8% 0f the Mn, 88.3% Of the CO, and 72.1% of the Ni.