Galena

PbS

by Blake Bentley



Provenance
Composition
Physical Properties
Crystallography

Optical Properties
XRD
Pictures

References
Links



Provenance:
Many minerals have their own aesthetic qualities, but few have the bright metallic shine of galena. Galena is most commonly found in lead sulfide veins. It also occurs disseminated in igneous and sedimentary rocks. The largest lead-mining district in the world is located in southeast Missouri. Other important regions are the Old Lead Belt, Fredericktown, Indian Creek, Higdon, Viburnum Trend, and the Joplin district of Missouri. These deposits are concentrated on either side of a Precambrian high, the Ozark dome, which forms the St. Francois Mountains (Emineral show). Galena occurs in many different types of deposits, often in metalliferous veins, as at Broken Hill, Australia; Coeur d'Alene, Idaho, U.S.; and Cornwall, England (Mineral Identification).  Galena has also been mined locally from the Berkeley Pit in Butte.

Galena
is the most significant lead mineral. It is used in car batteries, as solder, and in communication devises. All major radioactive elements (such as uranium) break down and create lead as one of their end products. Interestingly, lead is used to safely store radioactive materials because it absorbs radiation from the radioactive isotopes (Mineral Information Institute).

Galena was first mentioned by the Roman naturalist Caius Plinius Secundus, (AD 23August 24, AD 79), better known as Pliny the Elder, he used it to describe lead ore. One of the earliest uses of galena was as kohl (early form of mascara), which in Ancient Egypt was applied around the eyes to reduce the glare of the desert sun and to repel flies (Metropolitan Museum of Art).


Some varieties of galena include Argentiferous Galena, a mixture of galena and silver, Auriferous Galena is a gold-bearing variety of galena, a pseudomorph after Pyromorphite is Plumbein, and U-Galena is a variety of galena containing uranium-derived lead of isotope Pb-206.

A mineral simmilar to galena includes Iron pyrite Fe(II)S22-

 Want to know something else about galena? The lead it contains is a chemical known to the State of California to cause cancer, birth defects or other reproductive harm.

Composition:
Chemical Formula Pb(II)S
Molecular Weight 239.27 gm/mole
Lead(II) 86.60% Pb
Sulfur 13.40% S
Total 100.00%

Physical Properties:

          Luster- metallic, dull

          Transparency- opaque

          Hardness- 2.5

          Streak- lead gray  

          Color- lead gray

          Tenacity- brittle

          Cleavage- perfect [001]

          Density- 7.58 g/cm^3

          Specific gravity- 7.58

          Fracture- sub-conchoidal

          Crystal system- isometric 4/3 2/m

          Morphology- cubes, octahedrons

          Twinning- lamellar



Crystallography:
-Member of the isometric-hexoctahedral crystal system
-Most often form a cubic display with octahedral modifications
-Point group - 4/m32/m
-Space group fm3m 

Cell dimensions 
a = 5.936 angstroms
b = 5.936 angstroms
c = 5.936 angstroms
Total Volume 209.16 angsrtoms^3
The angles between the three axes are 90 degrees.

Optical Properties:
White
Galena
is a dense opaque mineral giving it limited optical properties. This minerals Reflected Light color is white and is isotropic. Scientists use microscopy in search of RL color for opaque minerals to determine the paragenetic relationships between different mineral phases and their identification

 
XRD:


 
 
Pictures:


References:

Emineral Show. A Guide to the Identification of Minerals of Missouri's Lead Mines. Http://www.emineralshow.com/mo_deposits.htm.Updated Dec. 30, 2001. Accessed on October 2007

 

Dave Jessey, and Don Tarman. Mineral Identification: The Beauty of Nature. Http://geology.csupomona.edu/alert/mineral/galena.htm. Accessed on October 2007

 

David Barthelmyupdate. Mineralogy Database. Http://webmineral.com. Updated 7/22/07. Accessed on October 2007

 

Metropolitan Museum of Art. The Art of Medicine in Ancient Egypt. New York: The Museum, 2005, pg. 10. Accessed on November 2007

 

Mineral Information Institute. Lead. http://www.mii.org/Minerals/photolead.html. Accessed on November 2007


Links
Web Mineral description of Galena

Wikapedia Galena Information