Red monoclinic crystals; MP 80 °C; density 1.59 g/cu cm; soluble in water and ethanol. /Tetrahydrate/;Cinnamon brown crystal solid; decomposes in water. /Dihydrate/;Pink crystals; soluble in methanol; dehydrates between 80-130 °C; decomposes at 350 °C to manganese(III) oxide. /Tetrahydrate/