Galena

From New World Encyclopedia
Revision as of 14:22, 24 April 2007 by Jeff Anderson (talk | contribs) ({{Contracted}})
For other uses, see Galena (disambiguation).
Galena
GalenaFromKansas.jpg
General
CategorySulfides
Chemical formulalead sulfide (PbS)
Identification
ColorLead gray, silvery
Crystal habitCubes and octahedra, tabular and sometimes skeletal crystals
Crystal systemIsometric hexoctahedral
CleavageCubic
FractureFlat (when cubic) to even
Mohs Scale hardness2.5 - 2.75
LusterMetallic
Refractive indexOpaque
PleochroismNone
StreakLead gray
Specific gravity7.4 - 7.6
Fusibility2

Galena is the natural mineral form of lead sulfide. It is one of the most abundant and widely distributed sulfide minerals.

It is the most important lead ore mineral.


Lead ore deposits

It is often associated with the minerals sphalerite, calcite and fluorite.

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. In addition zinc, cadmium, antimony, arsenic and bismuth also occur in variable amounts in lead ores. Selenium substitutes for sulfur in the structure constituting a solid solution series. The lead telluride mineral altaite has the same crystal structure as galena. Within the weathering or oxidation zone galena alters to anglesite (lead sulfate) or cerussite (lead carbonate).

File:Galena Poland.jpg
Galena from Poland

Galena deposits are found in France, Romania, Austria, Belgium, Italy, Spain, Scotland, England, Australia, and Mexico. Noted deposits include those at Freiberg, Saxony; Cornwall, Derbyshire, and Cumberland, England; the Sullivan mine of British Columbia; and Broken Hill, Australia. Galena also occurs at Mount Hermon in Northern Israel. In the United States it occurs most notably in the Mississippi Valley type deposits of the Lead Belt in southeastern Missouri, and in similar environments in Illinois, Iowa and Wisconsin. Galena also was a major mineral of the zinc-lead mines of the tri-state district arpond Joplin in southwestern Missouri and the adjoining areas of Kansas and Oklahoma. Galena is also an important ore mineral in the silver mining regions of Colorado, Idaho, Utah and Montana. Of the latter, the Coeur d'Alene district of northern Idaho was most prominent.

Galena is the official state mineral of the states of Missouri and Wisconsin.

Characteristics

It crystallizes in the cubic crystal system often showing octahedral forms.


Uses

File:Fluorite galena09.jpg
Dark gray cubes of galena with fluorite (purple) and calcite (white) from Illinois, USA

One of the earliest 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, a potential source of disease.[1]

Galena is a semiconductor with a small bandgap of 0.4 eV. In the early days of wireless, it was used as the 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. Scientists linked to this application were Karl Ferdinand Braun and Sir Jagdish Chandra Bose.

See also

Notes

  1. Metropolitan Museum of Art. The Art of Medicine in Ancient Egypt. (New York: The Museum, 2005), p. 10. ISBN 1-58839-170-1.

References
ISBN links support NWE through referral fees

  • Farndon, John. 2006. The Practical Encyclopedia of Rocks & Minerals: How to Find, Identify, Collect and Maintain the World's best Specimens, with over 1000 Photographs and Artworks. London: Lorenz Books. ISBN 0754815412.
  • Klein, Cornelis, and Barbara Dutrow. 2007. Manual of Mineral Science. 23rd ed. New York: John Wiley. ISBN 978-0471721574.
  • Pellant, Chris. 2002. Rocks and Minerals. Smithsonian Handbooks. New York: Dorling Kindersley. ISBN 0789491060.
  • Shaffer, Paul R., Herbert S. Zim, and Raymond Perlman. 2001. Rocks, Gems and Minerals. Rev. ed. New York: St. Martin's Press. ISBN 1582381321.
  • Mindat.org. 2007. Galena. Mindat.org. Retrieved April 10, 2007.

External links

  • Galena. (Deposits at Franklin and Sterling Hill, New Jersey.) Retrieved April 10, 2007.
  • Lead. (Mineral Information Institute.) Retrieved April 10, 2007.

Credits

New World Encyclopedia writers and editors rewrote and completed the Wikipedia article in accordance with New World Encyclopedia standards. This article abides by terms of the Creative Commons CC-by-sa 3.0 License (CC-by-sa), which may be used and disseminated with proper attribution. Credit is due under the terms of this license that can reference both the New World Encyclopedia contributors and the selfless volunteer contributors of the Wikimedia Foundation. To cite this article click here for a list of acceptable citing formats.The history of earlier contributions by wikipedians is accessible to researchers here:

The history of this article since it was imported to New World Encyclopedia:

Note: Some restrictions may apply to use of individual images which are separately licensed.