The paper proposes an application called OxyEMG (Oxyspinel group End-Member Generator), which is an improved version of EMG. This tool allows for calculating the portions of 31 end-members of the oxyspinel group from data obtained with an electron microprobe. This is fundamental since this group of minerals is considered to be tectonic tracers; their integral composition should be taken into account and not only those end-members that make up the magnetite or ulvöspinel prisms.