Manganese(III) oxide a structure related to the spinel structure of MnO where the oxide ions are cubic close packed. This is similar to the relationship between γ-FeO and FeO. γ-MnO is ferrimagnetic with a Néel temperature of 39 K. Manganese(III) oxide Manganese(III) oxide is a chemical compound with the formula MnO. Heating MnO in air at below 800 °C produces α-MnO (higher temperatures produce MnO). γ-MnO can be produced by oxidation followed by dehydration of manganese(II) hydroxide. Many preparations of nano-crystalline MnO have been reported, for example syntheses involving oxidation of Mn salts or reduction of MnO. Manganese (III) oxide is formed
Manganese white magnesia alba (magnesium oxide), which provided the name magnesium for the free element when it was isolated much later. Several colorful oxides of manganese, for example manganese dioxide, are abundant in nature and have been used as pigments since the Stone Age. The cave paintings in Gargas that are 30,000 to 24,000 years old contain manganese pigments. Manganese compounds were used by Egyptian and Roman glassmakers, either to add to, or remove color from glass. Use as "glassmakers soap" continued through the Middle Ages until modern times and is evident in 14th-century glass from Venice. Because it was used