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Galena

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Galena is most abundant and widely found sulfide mineral and other name is lead glance .It is most important minerals of lead and silver. Crystal system is cubic, isometric system and xpl features not observed. It is often associated with the minerals sphalerite, calcite and fluorite.

Name: The name is derived from the Latin galena, a name originally given to lead ore.

Crystallography. Isometric; hexoctahedral. The most common form is the cube. The octahedron sometimes is present as truncations to the cube.. Dodecahedron and trisoctahedron rare.

Composition. Lead sulfide, PbS. Pb = 8 6 . 6 per cent, S = 13.4 per cent. Analyses almost always show the presence of silver. It may also contain small amounts of selenium, zinc , cadmium, antimony, bismuth , and copper.

Diagnostic Features: It can be easily recognized b y its good cleavage, high specific gravity , softness, and black streak

Alteration: By oxidation galena is converted into the sulfate anglesite, and the carbo nate cerussite

Chemical Properties

Chemical Classification Sulfide mineral, octahedral subgroup
Chemical Composition PbS

Galena Physical Properties

Color Lead gray and silvery
Streak             Lead gray
Luster Metallic on cleavage planes
Diaphaneity             Opaque
Mohs Hardness 2.5–2.75
Specific Gravity 7.2–7.6
Diagnostic Properties High specific gravity
Crystal System Cubic

Galena Optical Properties

Galene under the microscope
Crystal Habit Cubes and octahedra, blocky, tabular and sometimes skeletal crystals
Cleavage Cubic perfect, parting on
Color/Pleochroism Isotropic and opaque
Optical Extinction Isotropic and opaque
Twinning Contact, penetration and lamellar
Optic Sign Isotropic and opaque
Birefringence Isotropic and opaque
Relief Isotropic and opaque

Occurrence

Galena occurs in a number of environments, such as hydrothermal veins (formed under various temperatures), metamorphic deposits, and in pegmatites. Limestones and dolostones are common in host rocks.

Some of the minerals with which galena is associated are spharelite, marcasite, pyrite, chalcopyrite, siderite, silver minerals, dolomite, quartz, and many other hydrothermal minerals.

Galena Uses

  • It is by far the greatest ore of lead. The extraction process to remove the lead from the sulfur is very simple, thus lead has been extracted from Galena since the earliest times.
  • It from certain regions is rich in silver, and some specimens may contain as much as 20 percent silver. Because of this, silver-rich Galena is also an ore of silver. Another use of Galena was its importance in early radio devices.

References

• Bonewitz, R. (2012). Rocks and minerals. 2nd ed. London: DK Publishing.
• Dana, J. D. (1864). Manual of Mineralogy… Wiley.
• Handbookofmineralogy.org. (2019). Handbook of Mineralogy. [online] Available at: http://www.handbookofmineralogy.org [Accessed 4 Mar. 2019].
• Mindat.org. (2019): Mineral information, data and localities.. [online] Available at: https://www.mindat.org/ [Accessed. 2019].

Cite this article as: Geology Science. (2019). Galena. [online] Available at: http://geologyscience.com/minerals/galena/ [4th December 2019 ]
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