Molybdenite
| Molybdenite | |
|---|---|
 Euhedralmolybdenite on quartz, Molly Hill mine, Quebec, Canada. The large crystal is 15 mm across | |
| General | |
| Category | Sulfide mineral |
| Formula (repeating unit) | Molybdenum disulfide(MoS2) |
| IMA symbol | Mol[1] |
| Strunz classification | 2.EA.30 |
| Crystal system | Common, 2H polytype:hexagonal 3R polytype:trigonal |
| Crystal class | 2H polytype: dihexagonal dipyramidal (6/mmm) 3R polytype: Ditrigonal pyramidal (3m) |
| Space group | 2H polytype:P63/mmc 3R polytype:R3m |
| Unit cell | 2H polytype: a = 3.16 Å, c = 12.3 Å; Z = 2 3R polytype: a = 3.16 Å, c = 18.33 Å; Z = 3 |
| Identification | |
| Color | Black, lead-silvery gray |
| Crystal habit | Thin, 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 |
| Cleavage | Perfect on [0001] |
| Tenacity | Lamellae flexible, not elastic |
| Mohs scalehardness | 1–1.5 |
| Luster | Metallic |
| Streak | Bluish gray |
| Diaphaneity | Nearly opaque; translucent in thin flakes |
| Specific gravity | 4.73 |
| Pleochroism | Very strong |
| Fusibility | Infusible (decomposes at 1185 °C) |
| Other characteristics | It has a greasy feel and leaves marks on fingers |
| References | [2][3][4][5][6] |
Molybdeniteis amineralofmolybdenum disulfide,MoS2.Similar in appearance and feel tographite,molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet ofmolybdenumatoms sandwiched between sheets ofsulfuratoms. 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 ascleavage planes. Molybdenite crystallizes in thehexagonal crystal systemas the commonpolytype2H and also in thetrigonalsystem as the 3R polytype.[3][4][7]
Description
[edit]Occurrence
[edit]
Molybdenite occurs in high temperaturehydrothermaloredeposits. Its associated minerals includepyrite,chalcopyrite,quartz,anhydrite,fluorite,andscheelite.Important deposits include the disseminated porphyry molybdenum deposits atQuesta, New Mexicoand theHendersonandClimaxmines inColorado.Molybdenite also occurs inporphyry copperdeposits ofArizona,Utah,andMexico.
The elementrheniumis 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 byX-ray diffractiontechniques. Molybdenite ores are essentially the only source for rhenium. The presence of theradioactive isotoperhenium-187 and its daughter isotopeosmium-187 provides a usefulgeochronologicdating technique.
Features
[edit]
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 amatrix.
Uses
[edit]Molybdenite is an important ore of molybdenum, and is the most common source of the metal.[4]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 byfroth flotation,and then oxidized to form solublemolybdate.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.Ferromolybdenumis an important component of high strength and corrosion-resistant steel.
Semiconductor
[edit]Multilayer molybdenite flakes aresemiconductorswith anindirect bandgap.In contrast, monolayer flakes have a direct gap.[8]In the early years of the 20th century, molybdenite was used in some of the first crudesemiconductor diodes,calledcat's whisker detectors,which served as ademodulatorin earlycrystal radios.Monolayer molybdenite shows goodcharge carrier mobilityand can be used to create small or low-voltagetransistors.[9]The transistors can detect and emit light and may have future use inoptoelectronics.[10]
See also
[edit]- Powellite(calcium molybdate: CaMoO4)
- Rheniite(rhenium sulfide: ReS2)
- Wulfenite(lead molybdate: PbMoO4)
References
[edit]- ^Warr, L.N. (2021)."IMA–CNMNC approved mineral symbols".Mineralogical Magazine.85(3): 291–320.Bibcode:2021MinM...85..291W.doi:10.1180/mgm.2021.43.S2CID235729616.
- ^Mineralienatlas
- ^abHandbook of Mineralogy
- ^abcMindat.org
- ^Webmineral data for Molybdenite
- ^Dana's Manual of MineralogyISBN0-471-03288-3
- ^Molybdenite 3R on Mindat
- ^Mak, Kin Fai; Lee, Changgu; Hone, James; Shan, Jie; Heinz, Tony F. (24 Sep 2010)."Atomically Thin MoS2: A New Direct-Gap Semiconductor".Physical Review Letters.Vol. 105, no. 13.doi:10.1103/PhysRevLett.105.136805.
- ^"Molybdenite transistor is a first".8 Feb 2011. Archived fromthe originalon 10 December 2011.Retrieved12 February2011.
- ^First light from molybdenite transistors. 19 Apr 2013
External links
[edit]
Media related toMolybdeniteat Wikimedia Commons
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