Galena

From Free net encyclopedia

This article is about the mineral. For various cities and towns of that name, see Galena (disambiguation).

Galena
Image:GalenaFromKansas.jpg
General
Category	Mineral
Chemical formula	lead sulfide (PbS)
Identification
Colour	Lead gray, silvery
Crystal habit	Cubes, tabular and sometimes skeletal crystals
Crystal system	Isometric hexoctahedral
Cleavage	Cubic
Fracture	Flat (when cubic) to even
Mohs Scale hardness	2.5 - 2.75
Luster	Metallic
Refractive index	Opaque
Pleochroism	None
Streak	Lead gray
Specific gravity	7.4 - 7.6
Fusibility	2

Galena is a lead ore. This article describes Galena's mineral properties. In its chemically purified form, galena is known as lead sulfide; refer to that article for chemical and industrial uses.

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.

Image:Galena Poland.jpg

Galena deposits are found in Germany, 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.

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Uses

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.

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