Molybdenite is a
mineral
In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...
of
molybdenum disulfide
Molybdenum disulfide (or moly) is an inorganic compound composed of molybdenum and sulfur. Its chemical formula is .
The compound is classified as a transition metal dichalcogenide. It is a silvery black solid that occurs as the mineral molybdeni ...
,
Mo S2. Similar in appearance and feel to
graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on la ...
, molybdenite has a lubricating effect that is a consequence of its layered structure. The atomic structure consists of a sheet of
molybdenum
Molybdenum is a chemical element with the symbol Mo and atomic number 42 which is located in period 5 and group 6. The name is from Neo-Latin ''molybdaenum'', which is based on Ancient Greek ', meaning lead, since its ores were confused with lead ...
atoms sandwiched between sheets of
sulfur
Sulfur (or sulphur in British English) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formul ...
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.
Molybdenite crystallizes in the
hexagonal crystal system
In crystallography, the hexagonal crystal family is one of the six crystal families, which includes two crystal systems (hexagonal and trigonal) and two lattice systems (hexagonal and rhombohedral). While commonly confused, the trigonal crysta ...
as the common
polytype
In materials science, polymorphism describes the existence of a solid material in more than one form or crystal structure. Polymorphism is a form of isomerism. Any crystalline material can exhibit the phenomenon. Allotropy refers to polymorphism ...
2H and also in the
trigonal system as the 3R polytype.
[
]
Description
Occurrence
Molybdenite occurs in high temperature hydrothermal
Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...
ore deposits.
Its associated minerals include pyrite
The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Iron, FeSulfur, S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral.
Pyrite's metallic Luster (mineralogy), lust ...
, chalcopyrite, quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical f ...
, anhydrite, fluorite, and scheelite. Important deposits include the disseminated porphyry molybdenum deposits at Questa, New Mexico and the Henderson Henderson may refer to:
People
* Henderson (surname), description of the surname, and a list of people with the surname
*Clan Henderson, a Scottish clan
Places Argentina
*Henderson, Buenos Aires
Australia
*Henderson, Western Australia
Canada
* ...
and Climax
Climax may refer to:
Language arts
* Climax (narrative), the point of highest tension in a narrative work
* Climax (rhetoric), a figure of speech that lists items in order of importance
Biology
* Climax community, a biological community t ...
mines in Colorado
Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...
. Molybdenite also occurs in porphyry copper deposits of Arizona
Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...
, Utah
Utah ( , ) is a state in the Mountain West subregion of the Western United States. Utah is a landlocked U.S. state bordered to its east by Colorado, to its northeast by Wyoming, to its north by Idaho, to its south by Arizona, and to its ...
, and Mexico
Mexico (Spanish language, Spanish: México), officially the United Mexican States, is a List of sovereign states, country in the southern portion of North America. It is borders of Mexico, bordered to the north by the United States; to the so ...
.
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
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...
techniques. Molybdenite ores are essentially the only source for rhenium. The presence of the radioactive isotope rhenium-187 and its daughter isotope osmium
Osmium (from Greek grc, ὀσμή, osme, smell, label=none) is a chemical element with the symbol Os and atomic number 76. It is a hard, brittle, bluish-white transition metal in the platinum group that is found as a trace element in alloys, ...
-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
Matrix most commonly refers to:
* ''The Matrix'' (franchise), an American media franchise
** '' The Matrix'', a 1999 science-fiction action film
** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...
.
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
In chemistry a molybdate is a compound containing an oxoanion with molybdenum in its highest oxidation state of 6. Molybdenum can form a very large range of such oxoanions which can be discrete structures or polymeric extended structures, altho ...
. 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 semiconductor
A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way ...
s 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
Demodulation is extracting the original information-bearing signal from a carrier wave. A demodulator is an electronic circuit (or computer program in a software-defined radio) that is used to recover the information content from the modulated ...
in early crystal radio
A crystal radio receiver, also called a crystal set, is a simple radio receiver, popular in the early days of radio. It uses only the power of the received radio signal to produce sound, needing no external power. It is named for its most imp ...
s. Monolayer molybdenite shows good charge carrier mobility and can be used to create small or low-voltage transistor
upright=1.4, gate (G), body (B), source (S) and drain (D) terminals. The gate is separated from the body by an insulating layer (pink).
A transistor is a semiconductor device used to Electronic amplifier, amplify or electronic switch, switch ...
s. The transistors can detect and emit light and may have future use in optoelectronics.First light from molybdenite transistors. 19 Apr 2013
/ref>
See also
*Powellite
Powellite is a calcium molybdate mineral with formula CaMoO4. Powellite crystallizes with tetragonal - dipyramidal crystal structure as transparent adamantine blue, greenish brown, yellow to grey typically anhedral forms. It exhibits distinct cl ...
(calcium molybdate: CaMoO4)
*Rheniite
Rheniite is a very rare rhenium sulfide mineral with the chemical formula ( ). It forms metallic, silver grey platey crystals in the triclinic - pinacoidal class. It has a specific gravity of 7.5.
It was discovered at the Kudriavy Volcano, Ituru ...
(rhenium sulfide: ReS2)
* Wulfenite (lead molybdate: PbMoO4)
References
External links
{{ores
Sulfide minerals
Molybdenum minerals
Non-petroleum based lubricants
Dry lubricants
Trigonal minerals
Minerals in space group 160
Hexagonal minerals
Minerals in space group 194
Semiconductor materials