Litharge

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.

It was first described as a mineral in 1917 for an occurrence in San Bernardino County, California.

Historically, the term "litharge" has been combined to refer to other similar substances. For example, litharge of gold is litharge mixed with red lead, giving it a red color; litharge of silver is litharge that comes as a by-product of separating silver from lead; litharge of bismuth is a similar result of the oxidation of bismuth. The term has also been used as a synonym for white lead or red lead.