Editing Quartz (section)

== Synthetic and artificial treatments ==
[[File:Quartz synthese (cropped).jpg|thumb|alt=A long, thin quartz crystal|left|A synthetic quartz crystal grown by the [[Hydrothermal synthesis|hydrothermal method]], about {{convert|19|cm}} long and weighing about {{convert|127|g}}]]
Not all varieties of quartz are naturally occurring. Some clear quartz crystals can be treated using heat or [[Gemstone irradiation|gamma-irradiation]] to induce color where it would not otherwise have occurred naturally. Susceptibility to such treatments depends on the location from which the quartz was mined.<ref>Liccini, Mark, [http://www.gemsociety.org/article/treating-quartz-color/ ''Treating Quartz to Create Color''] {{Webarchive|url=https://web.archive.org/web/20141223233321/http://www.gemsociety.org/article/treating-quartz-color/|date=23 December 2014}}, [[International Gem Society]] website. Retrieved 22 December 2014</ref>

Prasiolite, an olive colored material, is produced by heat treatment;<ref name="henn-etal-2012">{{cite journal|last1=Henn |first1=U. |last2=Schultz-Güttler |first2=R. |year=2012 |title=Review of some current coloured quartz varieties |journal=J. Gemmol |volume=33 |pages=29–43 |doi=10.15506/JoG.2012.33.1.29 |url=https://gem-a.com/images/Documents/JoG/JoG2012_33_1-4.pdf#page=31 |access-date=7 April 2021}}</ref> natural prasiolite has also been observed in Lower Silesia in Poland.<ref>{{cite journal |last1=Platonov |first1=Alexej N. |last2=Szuszkiewicz |first2=Adam |title=Green to blue-green quartz from Rakowice Wielkie (Sudetes, south-western Poland) – a re-examination of prasiolite-related color varieties of quartz |journal=Mineralogia |date=1 June 2015 |volume=46 |issue=1–2 |pages=19–28 |doi=10.1515/mipo-2016-0004|bibcode=2015Miner..46...19P |doi-access=free }}</ref> Although citrine occurs naturally, the majority is the result of heat-treating amethyst or smoky quartz.<ref name="henn-etal-2012"/> [[Carnelian]] has been heat-treated to deepen its color since prehistoric times.<ref>{{cite journal |last1=Groman-Yaroslavski |first1=Iris |last2=Bar-Yosef Mayer |first2=Daniella E. |title=Lapidary technology revealed by functional analysis of carnelian beads from the early Neolithic site of Nahal Hemar Cave, southern Levant |journal=Journal of Archaeological Science |date=June 2015 |volume=58 |pages=77–88 |doi=10.1016/j.jas.2015.03.030|bibcode=2015JArSc..58...77G }}</ref>

Because natural quartz is often [[crystal twinning|twinned]], synthetic quartz is produced for use in industry. Large, flawless, single crystals are synthesized in an [[Autoclave (industrial)|autoclave]] via the [[Hydrothermal synthesis|hydrothermal process]].<ref>{{cite journal |last1=Walker |first1=A. C. |title=Hydrothermal Synthesis of Quartz Crystals |journal=Journal of the American Ceramic Society |date=August 1953 |volume=36 |issue=8 |pages=250–256 |doi=10.1111/j.1151-2916.1953.tb12877.x}}</ref>{{sfn|Hurlbut|Klein|1985}}<ref name="buisson-arnaud-1994">{{cite journal |last1=Buisson |first1=X. |last2=Arnaud |first2=R. |title=Hydrothermal growth of quartz crystals in industry. Present status and evolution |journal=Le Journal de Physique IV |date=February 1994 |volume=04 |issue=C2 |pages=C2–25–C2-32 |doi=10.1051/jp4:1994204|s2cid=9636198 |url=https://hal.archives-ouvertes.fr/jpa-00252472/file/ajp-jp4199404C204.pdf }}</ref>

Like other crystals, quartz may be [[Metal-coated crystal|coated with metal vapors]] to give it an attractive sheen.<ref>{{Cite book | title = Gems: Their Sources, Descriptions and Identification | author = Robert Webster, Michael O'Donoghue | date = January 2006 | publisher = Butterworth-Heinemann | isbn = 9780750658560 | url = https://books.google.com/books?id=ZwcM5H-wHNoC&q=%22%222aqua+aura%22%222+-healing&pg=PT28 }}</ref><ref>{{cite web |title=How is Aura Rainbow Quartz Made? |url=http://www.geologyin.com/2017/06/how-is-aura-rainbow-quartz-made.html |website=Geology In |access-date=7 April 2021 |date=2017}}</ref>