Group: Sulfides

Chemical composition: PbS

Colors: Lead gray and silvery

Hardness: 2.5-3

Formation: Cubic, octahedra, tabular and sometimes skeletal crystals

Principal Sources: Worldwide

Special Notes: Galena deposits often contain significant amounts of silver as included silver sulfide mineral phases or as limited solid solution within the galena structure. These argentiferous galenas have long been the most important ore of silver in mining. Galena is the official state mineral of the U.S. states of Missouri and Wisconsin. One of the oldest uses of galena was as kohl, which in Ancient Egypt, was applied around the eyes to reduce the glare of the desert sun and to repel flies, which were a potential source of disease. Galena is a semiconductor with a small bandgap of about 0.4 eV which found use in early wireless communication systems. For example, it was used as the crystal in crystal radio sets