| Litharge | |
|---|---|
 | |
| General | |
| Category | Oxide minerals |
| Formula | PbO |
| IMA symbol | Lit[1] |
| Strunz classification | 4.AC.20 |
| Crystal system | Tetragonal |
| Crystal class | Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) |
| Space group | P4/nmm |
| Identification | |
| Color | red |
| Cleavage | Distinct/Good. On {110} |
| Mohs scale hardness | 2 |
| Luster | greasy, dull |
| Diaphaneity | transparent |
| References | [2][3][4] |
Litharge (from Greeklithargyros,lithos 'stone' +argyros 'silver'λιθάργυρος) is one of the natural mineral forms oflead(II) oxide, PbO. Litharge is asecondary mineral which forms from theoxidation ofgalenaores. It forms as coatings and encrustations with internaltetragonal crystal structure. It is dimorphous with the yelloworthorhombic formmassicot. It forms soft (Mohs hardness of 2), red, greasy-appearing crusts with a very highspecific gravity of 9.14–9.35. PbO may be prepared by heating lead metal in air at approximately 600 °C (lead melts at only 300 °C). At this temperature it is also the end product of heating of otherlead oxides in air.[5] This is often done with a set of bellows pumping air over molten lead and causing the oxidized product to slip or fall off the top into a receptacle, where it quickly solidifies in minute scales.[6]
Historically, the termlitharge has been combined to refer to other similar substances. For example, litharge ofgold is litharge mixed withred lead, giving it a red color; litharge of bismuth is a similar result of the oxidation ofbismuth; and litharge of silver is litharge that comes as a by-product of separating silver from lead. In fact,litharge originally meant the mineral residue from silver refining. The term has also been used as a synonym forwhite lead or red lead.[7]
According to Probert, "silverore, litharge (crude lead oxide)flux andcharcoal were mixed andsmelted in very smallclay and stonefurnaces. Resulting silver-bearing leadbullion was later refined in a second furnace which yielded fine silver, and litharge skimmings which were used again."[8]
