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Molybdenite

Molybdenite is the most important source of molybdenum, which is an important element in high-strength steels. Molybdenite was originally thought to be lead, and its name is derived from the Greek word for lead, molybdos. It was recognized as a distinct mineral by the Swedish chemist Carl Scheele in 1778. Molybdenite is soft, opaque, and bluish gray. It forms tabular hexagonal crystals, foliated masses, scales, and disseminated grains. It can also be massive or scaly. The platy, flexible, greasy-feeling hexagonal crystals of molybdenite can be confused with graphite, although molybdenite has a much higher specific gravity, a more metallic luster, and a slightly bluer tinge. Molybdenite occurs in granite, pegmatite, and hydrothermal veins at high temperature (1,065°F/575°C or above) with other minerals fluorite, ferberite, scheelite, and topaz. It is also found in porphyry ores and in contact metamorphic deposits.

Name: A word derived from the Greek molybdos, lead.

Chemistry: Nearly pure MoS2.

Polymorphism & Series: Dimorphous with jordisite; polytypes 2H1 and 3R are known.

Association: Chalcopyrite, other copper sulfides.

Chemical Properties of Molybdenite

Chemical Classification Sulfide mineral
Chemical Composition MoS2

Physical Properties of Molybdenite

Color Black, lead-silvery gray
Streak Bluish gray
Luster Metallic
Cleavage Perfect Perfect on {0001}
Diaphaneity Nearly opaque; translucent in thin flakes 
Mohs Hardness 1–1.5
Specific Gravity 4.73
Diagnostic Properties It has a greasy feel and leaves marks on fingers
Crystal System hexagonal
Tenacity Flexible
Density 4.62 – 4.73 g/cm3 (Measured)    4.998 g/cm3 (Calculated)

Optical Properties of
Molybdenite

Type Anisotropic
Anisotropism Very strong
Color / Pleochroism Strong

Occurrence

Molybdenite takes place in excessive temperature hydrothermal ore deposits. Its associated minerals consist of pyrite, chalcopyrite, quartz, anhydrite, fluorite, and scheelite. Important deposits include the disseminated porphyry molybdenum deposits at Questa, New Mexico and the Henderson and Climax mines in Colorado. Molybdenite also occurs in porphyry copper deposits of Arizona, Utah, and Mexico.

The element rhenium is continually found in molybdenite alternatively for molybdenum, generally inside the parts in step with million (ppm) variety, however frequently up to at least one–2%. High rhenium content material outcomes in a structural variety detectable through X-ray diffraction strategies. Molybdenite ores are essentially the best supply for rhenium. The presence of the radioactive isotope rhenium-187 and its daughter isotope osmium-187 provides a beneficial geochronologic relationship approach.

Uses Area

Molybdenite is an essential ore of molybdenum, and is the most common source of the metal.[3] While molybdenum is uncommon inside the Earth’s crust, molybdenite is tremendously common and smooth to system, and money owed for much of the metallic’s economic viability. Molybdenite is purified by way of froth flotation, after which oxidized to shape soluble molybdate. Reduction of ammonium molybdate yields pure molybdenum metal, that’s used for fertilizer, as a catalyst, and in battery electrodes. By a ways the maximum commonplace use of molybdenum is as an alloy with iron. Ferromolybdenum is an essential component of excessive strength and corrosion-resistant metallic.

Distribution

Of widespread occurrence; the most abundant molybdenum mineral.

  • Fine crystals occur, in the USA, at the Crown Point mine, Lake Chelan, Chelan Co., Washington; and at the Frankford quarry, Philadelphia, Pennsylvania.
  • In Canada, in the Temiskaming district, and in Aldfield Township, Quebec.
  • In Norway, from Raade, near Moss, and at Vennesla, near Arendal.
  • In Russia, in the Adun-Chilon Mountains, south of Nerchinsk, Transbaikal; at Miass, Ilmen Mountains, Southern Ural Mountains; and in the Slundyanogorsk deposit, Central Ural Mountains.
  • In Germany, at Altenberg, Saxony.
  • In Morocco, at Azegour, 80 km southwest of Marrakesh.
  • From Kingsgate and Deepwater, New South Wales, Australia.
  • At the Hirase mine, Gifu Prefecture, Japan.
  • In the Wolak mine, Danyang, Chungchong Province, South Korea.
  • The 3R polytype occurs in the Con mine, Yellowknife, Yukon Territory; and at Mont Saint-Hilaire, Quebec, Canada.
  • From the Yamate mine, Okayama Prefecture, Japan.

References

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