Manganese brown is considered to be mostly the mixed oxide of manganese with the formula Mn3O4. The name was sometimes used for organic brown pigments or for umber. The pigment is not affected by light.
PBr 8, CI 77727As the name of a black mineral, oxide of manganese (used from ancient times in glassmaking for removing coloring matter), from French manganèse (16c.), from Italian manganese, alteration or corruption of Medieval Latin magnesia.From Online Etymology Dictionary
The pigment can be prepared by mixing an aqueous solution of a manganese salt such as chloride or sulfate with a solution of sodium hypochlorite. The resulting insoluble pigment is then filtered, dried, and homogenized in a mortar.The mineral hausmannite has the same chemical composition as the pigment.
Manganese brown was described by the Roman historian and writer Pliny but was then considered to be iron ore.