a method for selectively extracting metal values from manganese bearing ores such as marine nodules . the ore is initially leached to solubilize manganese and other desirable metals as nitrates . the resulting solution is then treated with manganous hydroxide to selectively precipitate metals such as copper , nickel and cobalt . the enriched mixture of metal hydroxides is separated from the manganese nitrate solution , which is decomposed to recover high purity mno 2 .