In coal-based chemical looping combustion (CLC) technology, relatively cheap metal oxides, referred to as oxygen carrier materials (OCMs), are required because some of the OCMs will be removed together with the residual ashes after combustion. CLC technology will have an estimated loss in efficiency of around 2% compared to standard combustion technology without capture if a proper OCM is found that can give full combustion, removing the need of an air separation unit (ASU). Materials with a chemical looping oxygen uncoupling (CLOU) effect will even give further benefits in faster gasification and combustion of the fuel. One can already find produced materials that can give such a desirable effect, but fabrication and material cost are still an issue in these cases. If such a material can be delivered by the mining industry, cost savings and plant efficiency will be high. Before selection of the natural minerals with strong inert inherent support that contain Fe and Mn, the need for a better understanding of the Fe–Mn system is needed. This pre-study combined with other literature findings of the Fe–Mn system shows that a Mn content of up to 25–33% will increase the CLOU effect, increase the conversion of CH4, and give possibilities for full combustion in a CLC plant.