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Molybdenite



Molybdenite

General
CategoryMineral
Chemical formulamolybdenum sulfide:MoS2
Identification
ColorBlack, lead-silvery gray
Crystal habitThin, platy hexagonal crystals terminated by pinacoidal faces, also as tapering six-sided pyramids that can be truncated by the pinacoids. Also massive, lamellar and in small grains in sulfide ore bodies
Crystal systemHexagonal; 6/m 2/m 2/m
Cleavage[0001] Perfect
Fractureflaky
Mohs Scale hardness1 - 1.5
LusterMetallic
Refractive indexOpaque
Streakbluish - gray
Specific gravity4.73
FusibilityInfusible
Other CharacteristicsThin cleavage sheets and crystals are flexible, but not elastic. It has a greasy feel and leaves marks on fingers

Molybdenite is a mineral of molybdenum disulfide, MoS2. Similar in appearance and feel to graphite, molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet of molybdenum atoms sandwiched between sheets of sulfide atoms. The Mo-S bonds are strong, but the interaction between the sulfur atoms at the top and bottom of separate sandwich-like tri-layers is weak, resulting in easy slippage as well as cleavage planes.

Additional recommended knowledge

Associated minerals include pyrite, chalcopyrite, quartz, anhydrite, fluorite, and scheelite. Occurs in high temperature hydrothermal ore deposits. Important deposits include the disseminated porphyry molybdenum deposit at Questa, New Mexico and Climax, Colorado. Molybdenite also occurs in porphyry copper deposits of Arizona, Colorado, Utah, and Mexico.

The element rhenium is always present in molybdenite as a substitute for molybdenum usually in the parts per million (ppm) range, but often up to 1-2%. High rhenium content results in a structural variety detectable by X-ray diffraction techniques. Molybdenite ores are essentially the only source for rhenium. The presence of the radioactive isotope rhenium-187 and its daughter isotope osmium-187 provides a useful geochronologic dating technique.

References and external links

  • Dana's Manual of Mineralogy ISBN 0-471-03288-3
  • Mineralgalleries.com
  • Webmineral
  • Mindat.org
  • Molybdenite Dating
 
This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Molybdenite". A list of authors is available in Wikipedia.
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