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The U.S . Bureau of Mines conducted laboratory-scale research to determine the degree to which U.S. ferruginous manganese resources can be reduced to produce an acceptable ferromanganese for alloying iron and steel. The objective was to evaluate the feasibility of prereduction (reduction prior to melting) of such resources as an alternative to direct smelting. As part of the Bureau's goal to recover metal values economically and efficiently from U.S. resources, ferruginous manganese oxide materials from five deposits were reduced with low-cost and lower grade carbonaceous reductants at temperatures ranging from 600°C to 1,050°C for holding periods from 30 min. to 90 min. Greater than 95% net reduction of the tetravalent and trivalent states of manganese to the divalent state (which represents a typical feed for an electric arc furnace producing ferromanganese) was achieved at 750°C using inexpensive blacksmith coal on samples that did not contain significant amounts of silica.

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