Molybdenite

Description

Occurrence

Molybdenite occurs in high temperature hydrothermal ore deposits. Its associated minerals include 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 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.

Features

Molybdenite is extremely soft with a metallic luster, and is superficially almost identical to graphite, to the point where it is not possible to positively distinguish between the two minerals without scientific equipment. It marks paper in much the same way as graphite. Its distinguishing feature from graphite is its higher specific gravity, as well as its tendency to occur in a matrix.

Uses

Molybdenite is an important ore of molybdenum, and is the most common source of the metal. While molybdenum is rare in the Earth's crust, molybdenite is relatively common and easy to process, and accounts for much of the metal's economic viability. Molybdenite is purified by froth flotation, and then oxidized to form soluble molybdate. Reduction of ammonium molybdate yields pure molybdenum metal, which is used for fertilizer, as a catalyst, and in battery electrodes. By far the most common use of molybdenum is as an alloy with iron. Ferromolybdenum is an important component of high strength and corrosion-resistant steel.

Semiconductor

Multilayer molybdenite flakes are semiconductors with an indirect bandgap. In contrast, monolayer flakes have a direct gap. In the early years of the 20th century, molybdenite was used in some of the first crude semiconductor diodes, called cat's whisker detectors, which served as a demodulator in early crystal radios. Monolayer molybdenite shows good charge carrier mobility and can be used to create small or low-voltage transistors. The transistors can detect and emit light and may have future use in optoelectronics.

References

References

1. Warr, L.N.. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine.
2. [https://www.mineralienatlas.de/lexikon/index.php/MineralData?mineral=Molybdenite Mineralienatlas]
3. [http://rruff.geo.arizona.edu/doclib/hom/molybdenite.pdf Handbook of Mineralogy]
4. [http://www.mindat.org/min-2746.html Mindat.org]
5. [http://webmineral.com/data/Molybdenite.shtml Webmineral data for Molybdenite]
6. Dana's Manual of Mineralogy {{ISBN. 0-471-03288-3
7. [http://www.mindat.org/min-2745.html Molybdenite 3R on Mindat]
8. (24 Sep 2010). "Atomically Thin MoS2: A New Direct-Gap Semiconductor". Physical Review Letters.
9. (8 Feb 2011). "Molybdenite transistor is a first".
10. [http://physicsworld.com/cws/article/news/2013/apr/19/first-light-from-molybdenite-transistors First light from molybdenite transistors. 19 Apr 2013]