This report investigates the deposition of carbon from natural gas onto manganese ore and the effect of reduction of the higher manganese oxides. Manganese ore has been heated in an argon atmosphere, before methane was purged through the ore. To distinguish the reduction caused by heat and methane, experiments where manganese oxide was only heated in argon was executed. The most interesting samples were further studied in an electron probe microscope. The contemporary deposition of carbon and reduction is discussed, and compared with results from the project completed in the course TMT4500 Material Technology Specialization Project.