Galena is one of the most abundant and widely distributed sulfide minerals, and is the most common ore of lead. Crystals are usually cubic, sometimes octahedral. It is often associated with the minerals sphalerite and fluorite. Galena deposits sometimes contain significant amounts of silver as an impurity, and these galenas have long been the most important ore of silver in mining.
Galena deposits are found in France, Romania, Austria, Belgium, Italy, Spain, Scotland, England, Australia, and Mexico. In the United States it occurs in Missouri, Illinois, Iowa, Kansas, Oklahoma, Colorado, Idaho, Utah, Montana, and Wisconsin. Galena is the official state mineral of Missouri and Wisconsin, USA. Galena also occurs at Mount Hermon in Northern Israel. In ancient Israel it was used to colour eyes blue.
Galena was once used as a semiconductor (i.e. the crystal) in crystal radio sets; combined with a safety pin or similar sharp wire (known as a “cat’s whisker”), the galena crystal became part of a point-contact diode used to detect radio signals.