Editing Rutile (section)

==Occurrence==
[[Image:2005rutile.PNG|thumb|left|Rutile output in 2005]]
Rutile is a common accessory mineral in high-temperature and high-pressure [[metamorphic rock]]s and in [[igneous rock]]s.

[[Thermodynamic]]ally, rutile is the most stable polymorph of TiO<sub>2</sub> at all temperatures, exhibiting lower total [[Thermodynamic free energy|free energy]] than [[metastable]] phases of anatase or brookite.<ref>
{{cite journal
| last1=Hanaor
| first1=D.&nbsp;A.&nbsp;H.
| last2=Assadi
| first2=M.&nbsp;H.&nbsp;N.
| last3=Li
| first3=S.
| last4=Yu
| first4=A.
| last5=Sorrell
| first5=C.&nbsp;C.
| title= Ab initio study of phase stability in doped TiO<sub>2</sub>
| journal= Computational Mechanics
| year=2012
| volume=50
| issue=2
| pages=185–94
| doi=10.1007/s00466-012-0728-4| arxiv=1210.7555
| bibcode=2012CompM..50..185H
| s2cid=95958719
}}</ref> Consequently, the transformation of the metastable TiO<sub>2</sub> polymorphs to rutile is irreversible. As it has the lowest [[Van der Waals surface|molecular volume]] of the three main polymorphs, it is generally the primary titanium-bearing phase in most high-pressure metamorphic rocks, chiefly [[eclogite]]s.

[[File:Quartz-159832.jpg|thumb|left|[[Rutilated quartz|Rutile in quartz]]]]
Within the igneous environment, rutile is a common accessory mineral in [[Intrusive rock|plutonic igneous rocks]], though it is also found occasionally in [[Extrusive rock|extrusive igneous rocks]], particularly those such as [[kimberlite]]s and [[lamproite]]s that have deep mantle sources. Anatase and brookite are found in the igneous environment, particularly as products of [[autogenic alteration]] during the cooling of plutonic rocks; anatase is also found in [[placer deposit]]s sourced from primary rutile.

[[File:Rutil.jpg|thumb|left|Milled rutile]]The occurrence of large specimen crystals is most common in [[pegmatite]]s, [[skarn]]s, and [[granite]] [[greisen]]s. Rutile is found as an accessory mineral in some [[metasomatism|altered igneous rocks]], and in certain [[gneiss]]es and [[schist]]s. In groups of acicular [[crystal]]s it is frequently seen penetrating [[quartz]] as in the {{lang|fr|fléches d'amour}} from [[Graubünden]], [[Switzerland]]. In 2005 the Republic of [[Sierra Leone]] in [[West Africa]] had a production capacity of 23% of the world's annual rutile supply, which rose to approximately 30% in 2008.