Manganese(III) oxide is a chemical compound with the formula Mn 2 O 3.It occurs in nature as the mineral bixbyite (recently changed to bixbyite-(Mn)) and is used in the production of ferrites and thermistors. Preparation and chemistry Heating MnO 2 in air at below 800 °C produces α-Mn 2 O 3 (higher temperatures produce Mn 3 O 4). γ-Mn 2 O 3 can be produced by oxidation followed …