Editing Molybdenum (section)

==Occurrence and production==
[[File:Molly Hill molybdenite.JPG|thumb|alt=Lustrous, silvery, flat, hexagonal crystals in roughly parallel layers sit flowerlike on a rough, translucent crystalline piece of quartz.|[[Molybdenite]] on quartz]]
Molybdenum is the [[Abundance of elements in Earth's crust|54th most abundant element in the Earth's crust]] with an average of 1.5 parts per million and the 25th most abundant element in the oceans, with an average of 10&nbsp;parts per billion; it is the 42nd most abundant element in the Universe.<ref name="nbb" /><ref name="Nostrand">{{cite book|contribution = Molybdenum|date = 2005|title = Van Nostrand's Encyclopedia of Chemistry|pages = 1038–1040|place= New York|publisher = Wiley-Interscience|isbn=978-0-471-61525-5|editor= Considine, Glenn D.}}</ref> The Soviet [[Luna 24]] mission discovered a molybdenum-bearing grain (1 × 0.6&nbsp;μm) in a [[pyroxene]] fragment taken from [[Mare Crisium]] on the [[Moon]].<ref>{{cite journal|url=http://www.minsocam.org/msa/AmMin/TOC/Abstracts/2002_Abstracts/Jan02_Abstracts/Jambor_p181_02.pdf|title=New mineral names|journal=American Mineralogist|volume=87|page=181|date=2002|author=Jambor, J.L.|display-authors=etal|access-date=2007-04-09|archive-url=https://web.archive.org/web/20070710054017/http://www.minsocam.org/msa/AmMin/TOC/Abstracts/2002_Abstracts/Jan02_Abstracts/Jambor_p181_02.pdf|archive-date=2007-07-10|url-status=live}}</ref> The comparative rarity of molybdenum in the Earth's crust is offset by its concentration in a number of water-insoluble ores, often combined with sulfur in the same way as copper, with which it is often found. Though molybdenum is found in such [[mineral]]s as [[wulfenite]] (PbMoO<sub>4</sub>) and [[powellite]] (CaMoO<sub>4</sub>), the main commercial source is [[molybdenite]] (Mo[[sulfur|S]]<sub>2</sub>). Molybdenum is mined as a principal ore and is also recovered as a byproduct of copper and tungsten mining.<ref name="CRCdescription2" />

The world's production of molybdenum was 250,000 tonnes in 2011, the largest producers being China (94,000&nbsp;t), the United States (64,000&nbsp;t), Chile (38,000&nbsp;t), Peru (18,000&nbsp;t) and Mexico (12,000&nbsp;t). The total reserves are estimated at 10 million tonnes, and are mostly concentrated in China (4.3&nbsp;Mt), the US (2.7&nbsp;Mt) and Chile (1.2&nbsp;Mt). By continent, 93% of world molybdenum production is about evenly shared between North America, South America (mainly in Chile), and China. Europe and the rest of Asia (mostly Armenia, Russia, Iran and Mongolia) produce the remainder.<ref name="USGS" />

[[File:Molybdenum world production.svg|thumb|World production trend]]

In molybdenite processing, the ore is first roasted in air at a temperature of {{convert|700|°C|°F}}. The process gives gaseous sulfur dioxide and the [[Molybdenum trioxide|molybdenum(VI) oxide]]:<ref name="Holl" />

:<chem>2MoS2 + 7O2 -> 2MoO3 + 4SO2</chem>

The resulting oxide is then usually extracted with aqueous ammonia to give ammonium molybdate:
:<chem>MoO3 + 2NH3 + H2O -> (NH4)2(MoO4)</chem>
Copper, an impurity in molybdenite, is separated at this stage by treatment with [[hydrogen sulfide]].<ref name="Holl" /> Ammonium molybdate converts to [[ammonium dimolybdate]], which is isolated as a solid. Heating this solid gives molybdenum trioxide:<ref name="ullmann">{{cite book|doi=10.1002/14356007.a16_655|chapter=Molybdenum and Molybdenum Compounds |title=Ullmann's Encyclopedia of Industrial Chemistry |year=2000 |last1=Sebenik |first1=Roger F. |last2=Burkin |first2=A. Richard |last3=Dorfler |first3=Robert R. |last4=Laferty |first4=John M. |last5=Leichtfried |first5=Gerhard |last6=Meyer-Grünow |first6=Hartmut |last7=Mitchell |first7=Philip C. H. |last8=Vukasovich |first8=Mark S. |last9=Church |first9=Douglas A. |last10=Van Riper |first10=Gary G. |last11=Gilliland |first11=James C. |last12=Thielke |first12=Stanley A. |isbn=3527306730 |s2cid=98762721 }}</ref>
: <chem>(NH4)2Mo2O7 -> 2MoO3 + 2NH3 + H2O</chem>
Crude trioxide can be further purified by sublimation at {{convert|1100|°C|°F}}.

Metallic molybdenum is produced by reduction of the oxide with hydrogen:
:<chem>MoO3 + 3H2 -> Mo + 3H2O</chem>

The molybdenum for steel production is reduced by the [[aluminothermic reaction]] with addition of iron to produce [[ferromolybdenum]]. A common form of ferromolybdenum contains 60% molybdenum.<ref name="Holl">{{cite book|publisher = Walter de Gruyter|date = 1985|edition = 91–100|pages = 1096–1104|isbn = 978-3-11-007511-3|title = Lehrbuch der Anorganischen Chemie|author=Holleman, Arnold F. |author2=Wiberg, Egon |author3=Wiberg, Nils}}</ref><ref>{{cite book|last = Gupta|first = C. K.|title = Extractive Metallurgy of Molybdenum|publisher = CRC Press|date= 1992|pages = 1–2|isbn = 978-0-8493-4758-0}}</ref>

Molybdenum had a value of approximately $30,000 per tonne as of August 2009. It maintained a price at or near $10,000 per tonne from 1997 through 2003, and reached a peak of $103,000 per tonne in June 2005.<ref>{{cite web|title = Dynamic Prices and Charts for Molybdenum|publisher = InfoMine Inc.|date = 2007|url = http://www.infomine.com/investment/charts.aspx?c=molybdenum&u=mt&submit1=Display+Chart&x=usd&r=15y#chart|access-date = 2007-05-07|archive-url = https://web.archive.org/web/20091008202153/http://www.infomine.com/investment/charts.aspx?c=molybdenum&u=mt&submit1=Display+Chart&x=usd&r=15y#chart|archive-date = 2009-10-08|url-status = live}}</ref> In 2008, the [[London Metal Exchange]] announced that molybdenum would be traded as a commodity.<ref>{{cite web |title=LME to launch minor metals contracts in H2 2009 |url=http://www.lme.com/6241.asp |date=2008-09-04 |publisher=London Metal Exchange |access-date=2009-07-28 |archive-url=https://web.archive.org/web/20120722014344/http://www.lme.com/6241.asp |archive-date=2012-07-22 }}</ref>

===Mining===
The [[Knaben]] mine in southern Norway, opened in 1885, was the first dedicated molybdenum mine. Closed in 1973 but reopened in 2007,<ref>{{cite journal |doi = 10.1016/S0375-6742(96)00069-6 |title = Dispersion of tailings in the Knabena—Kvina drainage basin, Norway, 1: Evaluation of overbank sediments as sampling medium for regional geochemical mapping |date = 1997 |last1 = Langedal |first1 = M. |journal = Journal of Geochemical Exploration |volume = 58 |pages= 157–172 |issue = 2–3|bibcode = 1997JCExp..58..157L }}</ref> it now produces {{Convert|100000|kg|ton|0}} of molybdenum disulfide per year. Large mines in Colorado (such as the [[Henderson molybdenum mine|Henderson mine]] and the [[Climax mine]])<ref>{{cite journal|first= Paul B. |last = Coffman |title = The Rise of a New Metal: The Growth and Success of the Climax Molybdenum Company |journal = The Journal of Business of the University of Chicago |page= 30|date = 1937 |volume = 10 |doi = 10.1086/232443}}</ref> and in British Columbia yield molybdenite as their primary product, while many [[porphyry copper]] deposits such as the [[Bingham Canyon Mine]] in Utah and the [[Chuquicamata]] mine in northern Chile produce molybdenum as a byproduct of copper-mining.