Galena
From Wikipedia, the free encyclopedia
| Galena | |
|---|---|
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| General | |
| Category | Sulfides |
| Chemical formula | lead sulfide (PbS) |
| Identification | |
| Color | 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 the natural mineral form of lead sulfide. It is the most important lead ore mineral.
Galena is one of the most abundant and widely distributed sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms. It is often associated with the minerals sphalerite, calcite and fluorite.
Contents |
[edit] Lead ore deposits
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).
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 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 Missouri and Wisconsin, USA.
[edit] Uses
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 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.
[edit] See also
- List of minerals
- The Lead Belt, a major galena mining region in Missouri.
- lead
- Lead sulfide
[edit] References
- Klein, Cornelis and Cornelius S. Hurlbut, Jr. (1985) Manual of Mineralogy, Wiley, 2nd ed., pp. 274-276, ISBN 0-471-80580-7
- Webmineral data
- Mindat with location data
- Franklin and Sterling Hill mineral deposits
- Mineral Data Publishing - PDF
[edit] Notes
- ^ Metropolitan Museum of Art. The Art of Medicine in Ancient Egypt. (New York: The Museum, 2005), p. 10, ISBN 1-58839-170-1
