Editing Barium (section)

==Occurrence and production==
The abundance of barium is 0.0425% in the Earth's crust and 13&nbsp;μg/L in sea water. The primary commercial source of barium is [[baryte]] (also called barytes or heavy spar), a barium sulfate mineral.<ref name="Ullman2005" />{{rp|5}} with deposits in many parts of the world. Another commercial source, far less important than baryte, is [[witherite]], barium carbonate. The main deposits are located in Britain, Romania, and the former USSR.<ref name="Ullman2005" />{{rp|5}}

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The baryte reserves are estimated between 0.7 and 2 billion [[tonne]]s. The highest production, 8.3 million tonnes, was achieved in 1981, but only 7–8% was used for barium metal or compounds.<ref name="Ullman2005" />{{rp|5}} Baryte production has risen since the second half of the 1990s from 5.6 million tonnes in 1996 to 7.6 in 2005 and 7.8 in 2011. China accounts for more than 50% of this output, followed by India (14% in 2011), Morocco (8.3%), US (8.2%), Iran and Kazakhstan (2.6% each) and Turkey (2.5%).<ref>Miller, M. M. [http://minerals.usgs.gov/minerals/pubs/commodity/barite/mcs-2012-barit.pdf Barite]. USGS.gov</ref>

The mined ore is washed, crushed, classified, and separated from quartz. If the quartz penetrates too deeply into the ore, or the iron, zinc, or lead content is abnormally high, then [[froth flotation]]<!--https://books.google.com/books?id=zNicdkuulE4C&pg=PA223--> is used. The product is a 98% pure baryte (by mass); the purity should be no less than 95%, with a minimal content of iron and [[silicon dioxide]].<ref name="Ullman2005" />{{rp|7}} It is then reduced by carbon to [[barium sulfide]]:<ref name="Ullman2005" />{{rp|6}}
:BaSO<sub>4</sub> + 2 C → BaS + 2 CO<sub>2</sub>

The water-soluble barium sulfide is the starting point for other compounds: treating BaS with oxygen produces the sulfate, with nitric acid the nitrate, with aqueous carbon dioxide the carbonate, and so on.<ref name="Ullman2005" />{{rp|6}} The nitrate can be thermally decomposed to yield the oxide.<ref name="Ullman2005" />{{rp|6}} Barium metal is produced by reduction with [[aluminium]] at {{convert|1100|C}}. The [[intermetallic compound]] BaAl<sub>4</sub> is produced first:<ref name="Ullman2005" />{{rp|3}}
:3 BaO + 14 Al → 3 BaAl<sub>4</sub> + Al<sub>2</sub>O<sub>3</sub>

BaAl<sub>4</sub> is an intermediate reacted with barium oxide to produce the metal. Note that not all barium is reduced.<ref name="Ullman2005" />{{rp|3}}
:8 BaO + BaAl<sub>4</sub> → Ba↓ + 7 BaAl<sub>2</sub>O<sub>4</sub>

The remaining barium oxide reacts with the formed aluminium oxide:<ref name="Ullman2005" />{{rp|3}}
:BaO + Al<sub>2</sub>O<sub>3</sub> → BaAl<sub>2</sub>O<sub>4</sub>

and the overall reaction is<ref name="Ullman2005" />{{rp|3}}
:4 BaO + 2 Al → 3 Ba↓ + BaAl<sub>2</sub>O<sub>4</sub>

Barium vapor is condensed and packed into molds in an atmosphere of argon.<ref name="Ullman2005" />{{rp|3}} This method is used commercially, yielding ultrapure barium.<ref name="Ullman2005" />{{rp|3}} Commonly sold barium is about 99% pure, with main impurities being strontium and calcium (up to 0.8% and 0.25%) and other contaminants contributing less than 0.1%.<ref name="Ullman2005" />{{rp|4}}

A similar reaction with silicon at {{convert|1200|C}} yields barium and [[barium metasilicate]].<ref name="Ullman2005" />{{rp|3}} Electrolysis is not used because barium readily dissolves in molten halides and the product is rather impure.<ref name="Ullman2005" />{{rp|3}}
[[File:Benitoite HD.jpg|thumb|Benitoite crystals on natrolite. The mineral is named for the [[San Benito River]] in [[San Benito County]] where it was first found.]]

===Gemstone===
The barium mineral, [[benitoite]] (barium titanium silicate), occurs as a very rare blue fluorescent gemstone, and is the official state gem of [[California]].

===Barium in seawater===

Barium exists in seawater as the Ba<sup>2+</sup> ion with an average oceanic concentration of 109 nmol/kg.<ref name="www.mbari.org">{{Cite web|title=Barium|url=https://www.mbari.org/wp-content/static/chemsensor/ba/barium.html|access-date=2020-11-24|website=www.mbari.org}}</ref> Barium also exists in the ocean as BaSO<sub>4</sub>, or barite.<ref name="Griffith-2012">{{Cite journal|last1=Griffith|first1=Elizabeth M.|last2=Paytan|first2=Adina|date=2012|title=Barite in the ocean – occurrence, geochemistry and palaeoceanographic applications|url=|journal=Sedimentology|language=en|volume=59|issue=6|pages=1817–1835|doi=10.1111/j.1365-3091.2012.01327.x|bibcode=2012Sedim..59.1817G| s2cid=28056031 |issn=1365-3091}}</ref>  Barium has a nutrient-like profile<ref>{{Cite web|title=Graph|url=https://www.mbari.org/wp-content/static/chemsensor/ba/bagraph.html|access-date=2020-11-24|website=www.mbari.org}}</ref> with a residence time of 10,000 years.<ref name="www.mbari.org" />

Barium shows a relatively consistent concentration in upper ocean seawater, excepting regions of high river inputs and regions with strong upwelling.<ref name="Hsieh-2017">{{Cite journal|last1=Hsieh|first1=Yu-Te|last2=Henderson|first2=Gideon M.|date=2017|title=Barium stable isotopes in the global ocean: Tracer of Ba inputs and utilization|url=https://doi.org/10.1016/j.epsl.2017.06.024|journal=Earth and Planetary Science Letters|volume=473|pages=269–278|doi=10.1016/j.epsl.2017.06.024|bibcode=2017E&PSL.473..269H}}</ref> There is little depletion of barium concentrations in the upper ocean for an ion with a nutrient-like profile, thus lateral mixing is important.<ref name="Hsieh-2017" /> Barium isotopic values show basin-scale balances instead of local or short-term processes.<ref name="Hsieh-2017" />