Litharge is one of the natural mineral forms of lead(II) oxide, PbO. Litharge is a secondary mineral which forms from the oxidation of galena ores. It forms as coatings and encrustations with internal tetragonal crystal structure. It is dimorphous with the orthorhombic form massicot. It forms soft (Mohs hardness of 2), red, greasy-appearing crusts with a very high specific gravity of 9.149.35.