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Galena

Galena crystal from Galena, Kansas
General
Category Sulfide mineral
Chemical formula lead sulfide (PbS)
Strunz classification II/C.15-40
Dana classification 2.8.1.1
Crystal symmetry 2/m 3 2/m
Identification
Color Lead gray, silvery
Crystal habit Cubes and octahedra, tabular and sometimes skeletal crystals
Crystal system Isometric cF8, SpaceGroup Fm-3m, No. 225
Twinning Contact and penetration
Cleavage Cubic
Fracture Subconchoidal
Mohs scale hardness 2.5 - 2.75
Luster Metallic
Streak Lead gray
Diaphaneity Opaque
Specific gravity 7.2 - 7.6
Fusibility 2
References [1][2]
Galena's unit cell
Galena from Polish Kolchoz Mine

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

Lead ore deposits

galenit from Czech National museum in Prague

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 exposed to acid mine drainage can be oxidized to anglesite by naturally occurring bacteria and archaea, in a process similar to bioleaching [3]

Galena deposits are found in Wales, Germany, France, Romania, Austria, Belgium, Italy, Spain, Scotland, Ireland, England, Australia, Mexico, and the United States. Noted deposits include those at Freiberg, Saxony; Cornwall,The Mendips, Somerset, 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 the Driftless Area of Illinois, Iowa and Wisconsin. The economic importance of galena to the early history of the Driftless Area was so great that one of the towns in the region was named Galena, Illinois.

Galena also was a major mineral of the zinc-lead mines of the tri-state district around 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 U. S. states of Missouri and Wisconsin.

The largest documented single crystal of galena measured 25 cm x 25 cm x 25 cm.[4]

Galena uses

galenit from Czech National museum in Prague

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, which were a potential source of disease.[5]

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, in which it was used as a point-contact diode to detect the radio signals. The galena crystal was used with a safety pin or similar sharp wire, which was known as a "cat's whisker". Making such wireless sets was a popular home hobby in Britain during the 1930s. Derbyshire was one of the main areas where Galena was mined. Scientists that were linked to this application are Karl Ferdinand Braun and Sir Jagdish Bose. In modern wireless communication systems, galena detectors have been replaced by more reliable semiconductor devices, though silicon point-contact microwave detectors still exist in the market.

See also

Notes

  1. ^ http://rruff.geo.arizona.edu/doclib/hom/galena.pdf Handbook of Mineralogy
  2. ^ http://www.webmineral.com/data/Galena.shtml Webmineral data
  3. ^ Hydrometallurgy. Kinetics and mechanism of the bacterial and ferric sulphate oxidation of galena
  4. ^ P. C. Rickwood (1981). "The largest crystals". American Mineralogist 66: 885–907. http://www.minsocam.org/ammin/AM66/AM66_885.pdf. 
  5. ^ Metropolitan Museum of Art. The Art of Medicine in Ancient Egypt. (New York: The Museum, 2005), p. 10, ISBN 1-58839-170-1

References

External links


Travel guide

Up to date as of January 14, 2010

From Wikitravel

There is more than one place called Galena:

United States of America

This article is a disambiguation page. If you arrived here by following a link from another page you can help by correcting it, so that it points to the appropriate disambiguated page.

1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

GALENA, an important ore of lead, consisting of lead sulphide (PbS). The mineral was mentioned by Pliny under this name, and it is sometimes now known as lead-glance (Ger. Bleiglanz). It crystallizes in the cubic system, and well-developed crystals are of common occurrence; the usual form is the cube or the cubo-octahedron (fig.). An important character, and one by which the mineral may always be recognized, is the perfect cubical cleavage, on which the lustre is brilliant and metallic. The colour of the mineral and of its streak is lead-grey; it is opaque; the hardness is 2 2 and the specific gravity 7.5. Twinned crystals are not common, but the presence of polysynthetic twinning is sometimes shown by fine striations running diagonally or obliquely across the cleavage surfaces. Large masses with a coarse or fine granular structure are of common occurrence; the fractured surfaces of such masses present a spangled appearance owing to the numerous bright cleavages.

The formula PbS corresponds with lead 86.6 and sulphur 13.4%. The mineral nearly always contains a small amount of silver, and sometimes antimony, arsenic, copper, gold, selenium, &c. Argentiferous galena is an important source of silver; this metal is present in amounts rarely exceeding %, and often less than o 03% (equivalent to 104 ounces per ton). Since argentite (Ag 2 S) is isomorphous with galena, it is probable that the silver isomorphously replaces lead, but it is to be noted that native silver has been detected as an enclosure in galena.

Galena is of wide distribution, and occurs usually in metalliferous veins traversing crystalline rocks, clay-slates and limestones, and also as pockets in limestones. It is often associated with blende and pyrites, and with calcite, fluorspar, quartz, barytes, chalybite and pearlspar as gangue minerals; in the upper oxidized parts of the deposits, cerussite and anglesite occur as alteration products. The mineral has occasionally been observed as a recent formation replacing organic matter, such as wood; and it is sometimes found in beds of coal. As small concretionary nodules, it occurs disseminated through sandstone at Kommern in the Eifel. In the lead-mining districts of Derbyshire and the north of England the ore occurs as veins and flats in the Carboniferous Limestone series, whilst in Cornwall the veins traverse clay-slates. In the Upper Mississippi lead region of Missouri, Illinois, Iowa and Wisconsin the ore fills large cavities or chambers in limestone.

Galena is met with at all places where lead is mined; of localities which have yielded finely crystallized specimens the following may be selected for mention: Derbyshire, Alston in Cumberland, Laxey in the Isle of Man (where crystals measuring almost a foot across have been found), Neudorf in the Harz, Rossie in New York and Joplin in Missouri. Good crystals have also been obtained as a furnace product.

Coarsely grained galena is used for glazing pottery, and is then known as "potters' ore" or alquifoux.

The galena group includes several other cubic minerals, such as argentite (q.v.). Mention may also be made here of clausthalite (lead selenide, PbSe) and altaite (lead telluride, PbTe), which, with their lead-grey colour and perfect cubic cleavage, closely resemble galena in appearance; these species are named after the localities at which they were originally found, namely, Klausthal in the Harz and the Altai mountains in Asiatic Russia. Altaite is of interest as being one of the tellurides found associated with gold. (L. J. S.)


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Simple English


Galena is the main ore of lead. It is mostly lead(II) sulphide.

Galena is one of the most common and widely used sulfide minerals. It crystallizes in the cubic crystal system often showing octahedral forms. It is often found with the minerals sphalerite, calcite and fluorite.









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