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 9.14–9.35. PbO may be prepared by heating lead metal in air at approx. 600°C (lead melts at only 300°C). At this temperature it is also the end product of oxidation of other
lead oxides in air. This is often done with a set of bellows pumping air over molten lead and causing the oxidized product to slip/ fall off the top into a receptacle where it quickly solidifies in minute scales.
- PbO2 –(293 °C)→ Pb12O19 –(351 °C)→ Pb12O17 –(375 °C)→ Pb3O4 –(605 °C)→ PbO