Quartz

{{short description|Mineral made of silicon and oxygen}} {{About|the mineral|the countertop material|Engineered quartz|other uses}} {{Use American English|date=October 2021}} {{Use dmy dates|date=June 2019}} {{Infobox mineral | name = Quartz | category = Tectosilicate minerals | group = Quartz group | image = Quartz Brésil.jpg | imagesize = | caption = Quartz crystal cluster from Brazil | formula = SiO2 | IMAsymbol = Qz<ref>{{Cite journal|last=Warr|first=L.N.|date=2021|title=IMA–CNMNC approved mineral symbols|journal=Mineralogical Magazine|volume=85|issue=3|pages=291–320|doi=10.1180/mgm.2021.43|bibcode=2021MinM...85..291W|s2cid=235729616|doi-access=free}}</ref> | molweight = {{chem molar mass|Si=1|O=2}} | strunz = 4.DA.05 (oxides) | dana = 75.01.03.01 (tectosilicates) | system = α-quartz: trigonal β-quartz: hexagonal | class = α-quartz: trapezohedral (class 3 2) β-quartz: trapezohedral (class 6 2 2)<ref name="Deer">{{cite book |last1=Deer |first1=W. A. |last2=Howie |first2=R.A. |last3=Zussman |first3=J. |title=An introduction to the rock-forming minerals |date=1966 |publisher=Wiley |location=New York |isbn=0-582-44210-9 |pages=340–355}}</ref> | symmetry = α-quartz: ''P3221'' (no. 154)<ref>{{cite journal |last1=Antao |first1=S. M. |last2=Hassan |first2=I. |last3=Wang |first3=J. |last4=Lee |first4=P. L. |last5=Toby |first5=B. H. |title=State-Of-The-Art High-Resolution Powder X-Ray Diffraction (HRPXRD) Illustrated with Rietveld Structure Refinement of Quartz, Sodalite, Tremolite, and Meionite |journal=The Canadian Mineralogist |date=1 December 2008 |volume=46 |issue=6 |pages=1501–1509 |doi=10.3749/canmin.46.5.1501}}</ref> β-quartz: ''P6222'' (no. 180) or ''P6422'' (no. 181)<ref>{{cite journal |last1=Kihara |first1=K. |journal=European Journal of Mineralogy |volume=2 |year=1990 |pages=63–77 |title=An X-ray study of the temperature dependence of the quartz structure|issue=1 |doi=10.1127/ejm/2/1/0063 |bibcode=1990EJMin...2...63K |hdl=2027.42/146327 |hdl-access=free }}</ref> | unit cell = a = 4.9133 Å, c = 5.4053 Å; Z = 3 | color = Colorless, pink, orange, white, green, yellow, blue, purple, dark brown, or black | habit = 6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive | twinning = Common Dauphine law, Brazil law, and Japan law | cleavage = none<ref>Berry, R. W., et al. “Quartz Cleavage and Quick Clays.” Science, vol. 184, no. 4133, 12 Apr. 1974, pp. 183–184, https://doi.org/10.1126/science.184.4133.183. Accessed 19 May 2025.</ref> | fracture = Conchoidal | tenacity = Brittle | mohs = 7 – lower in impure varieties (defining mineral) | luster = Vitreous – waxy to dull when massive | refractive = nω = 1.543–1.545 nε = 1.552–1.554 | opticalprop = Uniaxial (+) | birefringence = +0.009 (B-G interval) | pleochroism = None | streak = White | gravity = 2.65; variable 2.59–2.63 in impure varieties | density = | melt = 1670 °C (β tridymite); 1713 °C (β cristobalite)<ref name=Deer/> | fusibility = | diagnostic = | solubility = Insoluble at STP; 1 ppmmass at 400 °C and 500  lb/in2 to 2600 ppmmass at 500 °C and 1500 lb/in2<ref name=Deer/> | diaphaneity = Transparent to nearly opaque | other = Lattice: hexagonal, piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic) | var1 = Rock crystal | var1text = Clear | var2 = Milky quartz | var2text = White | var3 = Amethyst | var3text = Violet | var4 = Citrine | var4text = Yellow | var5 = Smoky quartz | var5text = Gray to black, brown | var6 = Rose quartz | var6text = Pink | references = <ref name=Mindat>[http://www.mindat.org/min-3337.html Quartz] {{Webarchive|url=https://web.archive.org/web/20051214053641/http://www.mindat.org/min-3337.html |date=14 December 2005 }}. Mindat.org. Retrieved 2013-03-07.</ref><ref name=Handbook>{{cite book |editor1=Anthony, John W. |editor2=Bideaux, Richard A. |editor3=Bladh, Kenneth W. |editor4=Nichols, Monte C. |title=Handbook of Mineralogy |publisher=Mineralogical Society of America |place=Chantilly, VA |chapter-url=http://rruff.geo.arizona.edu/doclib/hom/quartz.pdf |chapter=Quartz |date=29 January 1990 |isbn=0962209724 |volume=III (Halides, Hydroxides, Oxides) |access-date=21 October 2009 |archive-url=https://web.archive.org/web/20100401032832/http://rruff.geo.arizona.edu/doclib/hom/quartz.pdf |archive-date=1 April 2010 |url-status=live }}</ref><ref name=Webmin>[http://www.webmineral.com/data/Quartz.shtml Quartz] {{Webarchive|url=https://web.archive.org/web/20061112152609/http://webmineral.com/data/Quartz.shtml |date=12 November 2006 }}. Webmineral.com. Retrieved 2013-03-07.</ref><ref name=Klein>{{cite book|last1=Hurlbut |first1=Cornelius S.|last2=Klein |first2=Cornelis|year=1985|title=Manual of Mineralogy|publisher=Wiley |edition=20|isbn=0-471-80580-7|url-access=registration|url=https://archive.org/details/manualofmineralo00klei}}</ref> }}

'''Quartz''' is a hard mineral composed of silica (silicon dioxide). Its atoms are linked in a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen atom being shared between two tetrahedra, giving an overall chemical formula of SiO2. Therefore, quartz is classified structurally as a framework silicate mineral and compositionally as an oxide mineral. Quartz is the second most common mineral or mineral group in Earth's lithosphere, comprising about 12% by mass.

Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which are chiral. The transformation from α-quartz to β-quartz takes place abruptly at {{convert|573|C|K F}}. Since the transformation is accompanied by a significant change in volume, it can easily induce microfracturing of ceramics or rocks passing through this temperature threshold.

There are many different varieties of quartz, several of which are classified as gemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of jewelry and hardstone carvings, especially in Europe and Asia.

Quartz is the mineral defining the value of 7 on the Mohs scale of hardness, a qualitative scratch method for determining the hardness of a material.

== Etymology == The word ''quartz'' is derived from the German word {{Lang|de|Quarz}},<ref name="Merriam">{{cite web | url=https://www.merriam-webster.com/dictionary/quartz | title=Quartz | work=Merriam-Webster.com Dictionary | access-date=9 January 2024}}</ref> which had the same form in the first half of the 14th century in Middle High German and in East Central German<ref>{{Cite web |title=DWDS – Quarz |url=https://www.dwds.de/wb/Quarz |archive-url=https://web.archive.org/web/20171201042329/https://www.dwds.de/wb/Quarz |archive-date=2017-12-01 |access-date=2026-03-01 |website=www.dwds.de |language=de}}</ref> and which came from the Polish dialect term ''kwardy'', which corresponds to the Czech term {{Lang|cs|tvrdý}} ('hard').<ref>{{Cite web |url=https://en.oxforddictionaries.com/definition/quartz |title=Quartz | Definition of quartz by Lexico |access-date=26 November 2017 |archive-url=https://web.archive.org/web/20171201043652/https://en.oxforddictionaries.com/definition/quartz |archive-date=1 December 2017 |url-status=dead }}</ref> Some sources, however, attribute the word's origin to the Saxon word ''Querkluftertz'', meaning 'cross-vein ore'.<ref>{{usurped|1=[https://web.archive.org/web/20070904052949/http://www.mineralatlas.com/mineral%20general%20descriptions/Q/quartzpcd.htm Mineral Atlas]}}, Queensland University of Technology. Mineralatlas.com. Retrieved 2013-03-07.</ref><ref name="Tomkeieff">{{cite journal |author=Tomkeieff, S.I. |year=1942 |title=On the origin of the name 'quartz' |url=http://www.minersoc.org/pages/Archive-MM/Volume_26/26-176-172.pdf |url-status=dead |journal=Mineralogical Magazine |volume=26 |issue=176 |pages=172–178 |bibcode=1942MinM...26..172T |doi=10.1180/minmag.1942.026.176.04 |archive-url=https://web.archive.org/web/20150904013105/http://www.minersoc.org/pages/Archive-MM/Volume_26/26-176-172.pdf |archive-date=4 September 2015 |access-date=12 August 2015 |df=dmy-all}}</ref>

The Ancient Greeks referred to quartz as {{Lang|grc|κρύσταλλος}} ({{Transliteration|grc|krustallos}}) meaning 'crystal', derived from the Ancient Greek {{Lang|grc|κρύος}} ({{Transliteration|grc|kruos}}) meaning 'icy cold', because some philosophers (including Theophrastus) believed the mineral to be a form of supercooled ice.<ref name="Tomkeieff"/> Today, the term ''rock crystal'' is sometimes used as an alternative name for transparent, coarsely crystalline quartz.<ref>{{cite journal |last1=Morgado |first1=Antonio |last2=Lozano |first2=José Antonio |last3=García Sanjuán |first3=Leonardo |last4=Triviño |first4=Miriam Luciañez |last5=Odriozola |first5=Carlos P. |last6=Irisarri |first6=Daniel Lamarca |last7=Flores |first7=Álvaro Fernández |title=The allure of rock crystal in Copper Age southern Iberia: Technical skill and distinguished objects from Valencina de la Concepción (Seville, Spain) |journal=Quaternary International |date=December 2016 |volume=424 |pages=232–249 |doi=10.1016/j.quaint.2015.08.004|bibcode=2016QuInt.424..232M |hdl=10810/78341 |hdl-access=free }}</ref><ref name=Nesse>{{cite book |last1=Nesse |first1=William D. |title=Introduction to mineralogy |date=2000 |publisher=Oxford University Press |location=New York |isbn=9780195106916}}</ref>{{rp|205}}

== Early studies ==

Roman naturalist Pliny the Elder believed quartz to be ice, permanently frozen after great lengths of time.<ref>Pliny the Elder, ''The Natural History'', Book 37, Chapter 9. Available on-line at: [https://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137%3Abook%3D37%3Achapter%3D9 Perseus.Tufts.edu] {{Webarchive|url=https://web.archive.org/web/20121109044605/http://www.perseus.tufts.edu/hopper/text?doc=Perseus%3Atext%3A1999.02.0137%3Abook%3D37%3Achapter%3D9 |date=9 November 2012 }}.</ref> He supported this idea by saying that quartz is found near glaciers in the Alps, but not in warm climates. This idea persisted until at least the 17th century.<ref>{{cite journal |last1=Tutton |first1=A.E. |year=1910 |title=Rock crystal: its structure and uses |journal=RSA Journal |volume=59 |page=1091 |jstor=41339844}}</ref>

In the 17th century, Nicolas Steno's study of quartz paved the way for modern crystallography. He discovered that, regardless of a quartz crystal's size or shape, its long prism faces always meet at a perfect 60° angle, thereby establishing the law of constancy of interfacial angles.<ref>Nicolaus Steno (Latinized name of Niels Steensen) with John Garrett Winter, trans.. ''The Prodromus of Nicolaus Steno's Dissertation Concerning a Solid Body Enclosed by Process of Nature Within a Solid'' (New York, New York: Macmillan Co., 1916). On [https://books.google.com/books?id=5IYNAAAAYAAJ&pg=PA272 page 272] {{Webarchive|url=https://web.archive.org/web/20150904013105/https://books.google.com/books?id=5IYNAAAAYAAJ&pg=PA272 |date=4 September 2015 }}, Steno states his law of constancy of interfacial angles: "Figures 5 and 6 belong to the class of those which I could present in countless numbers to prove that in the plane of the axis both the number and the length of the sides are changed in various ways without changing the angles; … "</ref>

== Crystal habit and structure == {{multiple image |align=right |perrow=3 |total_width=450

|image1=Α-Quartz.svg |caption1=Crystal structure of α-quartz (red balls are oxygen, gray are silicon)

|image2=Β-Quartz.svg |caption2=Crystal structure of β-quartz

|image3=Alpha-quartz, P3 121 and P3 221.png |caption3=A chiral pair of α-quartz

}} Quartz can form as two distinct polymorphs depending on the temperature and pressure: ''α-quartz'' (also called ''low quartz'' or ''normal quartz'') and ''β-quartz'' (also called ''quartz-beta'' or ''high quartz''). α-quartz crystallizes in the trigonal crystal system, while β-quartz has greater symmetry and crystallizes in the hexagonal crystal system. The transition from α-quartz to β-quartz occurs abruptly at {{convert|573|C|F K}} at ambient pressure; the transition temperature is greater at higher pressures. β-quartz is unstable at room temperature; therefore, all quartz at room temperature is α-quartz regardless of which polymorph it formed as.<ref>{{cite web |title=Quartz-beta |url=https://www.mindat.org/min-7395.html |website=mindat.org |publisher=Hudson Institute of Mineralogy |access-date=8 December 2025}}</ref>

Both polymorphs of quartz can occur in two different space groups depending on the chirality. Above the transition temperature, α-quartz in ''P''3121 (space group 152) becomes β-quartz in ''P''6422 (space group 181), and α-quartz in ''P''3221 (space group 154) becomes β-quartz in ''P''6222 (space group 180).<ref>Crystal Data, Determinative Tables, ACA Monograph No. 5, American Crystallographic Association, 1963</ref>

These space groups are truly chiral (they each belong to the 11 enantiomorphous pairs). Both α-quartz and β-quartz are examples of chiral crystal structures composed of achiral building blocks (SiO4 tetrahedra in the present case). The transformation between α- and β-quartz only involves a comparatively minor rotation of the tetrahedra with respect to one another, without a change in the way they are linked.<ref name=Klein/>{{r|Nesse|p=201}} However, there is a significant change in volume during this transition,<ref>{{Cite journal |last1=Johnson |first1=Scott E. |last2=Song |first2=Won Joon |last3=Cook |first3=Alden C. |last4=Vel |first4=Senthil S. |last5=Gerbi |first5=Christopher C. |date=2021-01-01 |title=The quartz α↔β phase transition: Does it drive damage and reaction in continental crust? |journal=Earth and Planetary Science Letters |volume=553 |article-number=116622 |doi=10.1016/j.epsl.2020.116622 |bibcode=2021E&PSL.55316622J |issn=0012-821X|doi-access=free }}</ref> and this can result in significant microfracturing in ceramics during firing,<ref>{{cite journal |last1=Knapek |first1=Michal |last2=Húlan |first2=Tomáš |last3=Minárik |first3=Peter |last4=Dobroň |first4=Patrik |last5=Štubňa |first5=Igor |last6=Stráská |first6=Jitka |last7=Chmelík |first7=František |title=Study of microcracking in illite-based ceramics during firing |journal=Journal of the European Ceramic Society |date=January 2016 |volume=36 |issue=1 |pages=221–226 |doi=10.1016/j.jeurceramsoc.2015.09.004}}</ref> in ornamental stone after a fire<ref>{{Cite journal |last1=Tomás |first1=R. |last2=Cano |first2=M. |last3=Pulgarín |first3=L. F. |last4=Brotóns |first4=V. |last5=Benavente |first5=D. |last6=Miranda |first6=T. |last7=Vasconcelos |first7=G. |date=2021-11-01 |title=Thermal effect of high temperatures on the physical and mechanical properties of a granite used in UNESCO World Heritage sites in north Portugal |url=https://linkinghub.elsevier.com/retrieve/pii/S2352710221006811 |journal=Journal of Building Engineering |volume=43 |article-number=102823 |doi=10.1016/j.jobe.2021.102823 |issn=2352-7102|hdl=10045/115630 |hdl-access=free }}</ref> and in rocks of the Earth's crust exposed to high temperatures,<ref>{{cite journal |last1=Johnson |first1=Scott E. |last2=Song |first2=Won Joon |last3=Cook |first3=Alden C. |last4=Vel |first4=Senthil S. |last5=Gerbi |first5=Christopher C. |title=The quartz α↔β phase transition: Does it drive damage and reaction in continental crust? |journal=Earth and Planetary Science Letters |date=January 2021 |volume=553 |article-number=116622 |doi=10.1016/j.epsl.2020.116622|bibcode=2021E&PSL.55316622J |s2cid=225116168 |doi-access=free }}</ref> thereby damaging materials containing quartz and degrading their physical and mechanical properties.

The ideal crystal shape for quartz is a six-sided prism terminating with six-sided pyramid-like rhombohedrons at each end. In nature, quartz crystals are often twinned (with twin right-handed and left-handed quartz crystals), distorted, or so intergrown with adjacent crystals of quartz or other minerals as to only show part of this shape, or to lack obvious crystal faces altogether and appear massive.<ref name=Klein/>{{r|Nesse|p=202–204}}

Well-formed crystals typically form as a druse (a layer of crystals lining a void), of which quartz geodes are particularly fine examples.<ref name=sinkankas>{{cite book |last1=Sinkankas |first1=John |title=Mineralogy for amateurs. |date=1964 |publisher=Van Nostrand |location=Princeton, N.J. |isbn=0442276249 |pages=443–447}}</ref> The crystals are attached at one end to the enclosing rock, and only one termination pyramid is present. However, doubly terminated crystals do occur where they develop freely without attachment, for instance, within gypsum.<ref>{{cite journal|first1=W. A |last1=Tarr |title=Doubly terminated quartz crystals occurring in gypsum |journal=American Mineralogist |year=1929 |volume=14 |number=1 |pages=19–25 |url=https://pubs.geoscienceworld.org/msa/ammin/article-abstract/14/1/19/535468 |access-date=7 April 2021}}</ref>

<gallery class="center"> File:00026 40 mm quartz.jpg|Common, prismatic quartz File:Améthyste, quartz 300-3-7640.JPG|Sceptered quartz File:Quartz sceptres fumés sur quartz (Madagascar) 1.jpg|Sceptered quartz (as aggregates: "Elestial quartz") File:Quartz-314899.jpg|Bipyramidal quartz File:Quartz-197980.jpg|Tessin or tapered quartz File:Hyaline quartz-MCG-NM-IMG 7481-black.jpg|Twinned quartz (known as Japan law) File:Quartz sur quartz 7(Brésil).jpg|Dauphine quartz (single dominant face) File:Herkimer.jpg|"Herkimer diamond" File:Quartz crystals Macro 1.JPG|Druse quartz File:Chalcedony (48723879712).jpg|Granular quartz File:Rose quartz SiO2 locality - Dolní Bory, Czech Republic (50660502442).jpg|Massive quartz </gallery>

== Varieties == [[File:Transparency.jpg|thumb|Clear quartz crystal demonstrating transparency]] Pure quartz, traditionally called rock crystal or clear quartz, is colorless and transparent or translucent. Colored varieties of quartz are common and include citrine, rose quartz, amethyst, smoky quartz, milky quartz, and others.<ref>{{Cite web |title=Quartz: The gemstone Quartz information and pictures |url=http://www.minerals.net/gemstone/quartz_gemstone.aspx |archive-url=https://web.archive.org/web/20170827194835/http://www.minerals.net/gemstone/quartz_gemstone.aspx |archive-date=2017-08-27 |access-date=2026-03-01 |website=www.minerals.net |language=en-US}}</ref> These color differentiations arise from the presence of impurities which change the molecular orbitals, causing some electronic transitions to take place in the visible spectrum, emitting colored light.{{citation needed|date=November 2025}}

Quartz varieties were previously classified into three categories based on the visibility of their individual crystals. Macrocrystalline quartz varieties have individual crystals that are visible to the unaided eye (macroscopic). Microcrystalline quartz varieties are aggregates of tiny crystals that can only be seen through a microscope (microscopic). Cryptocrystalline quartz varieties are aggregates of crystals that are too small to be seen even with an optical microscope (sub-microscopic).<ref name="The Quartz Page">{{cite web |last1=Akhavan |first1=Amir C. |title=Types of Quartz |url=http://www.quartzpage.de/gen_types.html |website=The Quartz Page |access-date=25 November 2025 |date=4 November 2011}}</ref> Today, the microcrystalline and cryptocrystalline varieties are commonly grouped together and referred to as chalcedony.<ref name="The Quartz Page" /><ref name="chalcedony">{{cite web |title=Chalcedony |url=https://www.mindat.org/min-960.html |publisher=Hudson Institute of Mineralogy |access-date=25 November 2025}}</ref> However, in the scientific literature, chalcedony is a specific form of silica consisting of fine intergrowths of both quartz and its monoclinic polymorph, moganite.<ref name="heany_1994">{{cite journal |last=Heaney |first=Peter J. |year=1994 |title=Structure and Chemistry of the low-pressure silica polymorphs |url=http://rimg.geoscienceworld.org/cgi/content/abstract/29/1/1 |url-status=live |journal=Reviews in Mineralogy and Geochemistry |volume=29 |issue=1 |pages=1–40 |archive-url=https://web.archive.org/web/20110724151910/http://rimg.geoscienceworld.org/cgi/content/abstract/29/1/1 |archive-date=24 July 2011 |access-date=26 October 2009}}</ref><ref name="chalcedony" /> Chalcedony is commonly translucent to opaque, while the macrocrystalline varieties of quartz tend to be more transparent.<ref name=":1">{{Cite web |title=Quartz Gemstone and Jewelry Information: Natural Quartz - GemSelect |url=https://www.gemselect.com/gem-info/quartz/quartz-info.php |archive-url=https://web.archive.org/web/20170829171847/https://www.gemselect.com/gem-info/quartz/quartz-info.php |archive-date=2017-08-29 |access-date=2026-03-01 |website=www.gemselect.com}}</ref><ref name="The Quartz Page" /> Color is a secondary identifier for the cryptocrystalline varieties and a primary identifier for the macrocrystalline varieties.<ref name=":1" />{{better source needed|date=November 2025}}

{{sticky header}} {| class="wikitable sortable sticky-header" | |+ Varieties of quartz |- ! Name !! Color !! Cause !! Description !! Crystal visibility !! Transparency !! Major sources !! Photo(s) !! References |- | Agate || Frequently multicolored; commonly colorless, pale blue to black, red to orange, yellow, white, brown, pink, purple; rarely green || Varies by color || Banded variety of chalcedony || Cryptocrystalline, microcrystalline || Translucent to opaque || Widespread || 150px Agate nodule from Malawi || <ref name="mindat">{{Cite web |title=Agate |url=https://www.mindat.org/min-51.html |access-date=26 November 2025 |website=mindat.org |publisher=Hudson Institute of Mineralogy}}</ref><ref name="pabian">{{Cite book |last1=Pabian |first1=Roger |title=Agates: Treasures of the Earth |last2=Jackson |first2=Brian |last3=Tandy |first3=Peter |last4=Cromartie |first4=John |date=2016 |publisher=Firefly Books |isbn=978-1-77085-644-8}}</ref> |- | Amethyst || Purple to violet || Natural irradiation and trace impurities of iron (Fe3+) || Commonly occurs in large clusters and geodes || Macrocrystalline || Transparent || Brazil, Mexico, Uruguay, Russia, France, Namibia, Morocco || 150px Amethyst cluster from Siberia || <ref>{{cite web |title=Amethyst |url=https://www.mindat.org/min-198.html |website=mindat.org |publisher=Hudson Institute of Mineralogy |access-date=25 November 2025}}</ref><ref>{{cite journal |last1=Lehmann |first1=G. |last2=Moore |first2=W. J. |title=Color Center in Amethyst Quartz |journal=Science |date=20 May 1966 |volume=152 |issue=3725 |pages=1061–1062 |doi=10.1126/science.152.3725.1061|pmid=17754816 |bibcode=1966Sci...152.1061L |s2cid=29602180 }}</ref> |- | Ametrine || Violet and yellow || Iron impurities || Commonly believed to be a combination of citrine and amethyst in the same crystal, although the yellow quartz component may not be true citrine. Most material sold as ametrine is partially heat-treated or artificially irradiated amethyst. || Macrocrystalline || Transparent to translucent || Bolivia, Brazil, India || 150px Rough ametrine from Bolivia 150px Cut ametrine || <ref>{{Cite web |title=Ametrine |url=https://www.mindat.org/min-7606.html |access-date=2025-01-10 |website=www.mindat.org}}</ref><ref name=":2">{{Cite web |title=Quartz (var. ametrine) {{!}} Smithsonian National Museum of Natural History |url=https://naturalhistory.si.edu/explore/collections/geogallery/10002876 |access-date=2025-01-10 |website=naturalhistory.si.edu |language=en}}</ref> |- | Carnelian || Orange to red, red-brown || Iron oxide impurities || Variety of chalcedony. Natural carnelian is usually light in color; darker colors are produced by artificial heat treatment. || Cryptocrystalline, microcrystalline || Translucent to opaque || Peru, Sri Lanka || 150px Natural carnelian from New Jersey, U.S. 150px Carnelian cabochons || <ref>{{cite web |last1=Ralph |first1=Jolyon |last2=Ralph |first2=Katya |title=Carnelian gemstone information |url=https://www.gemdat.org/gem-9333.html |website=gemdat.org |access-date=26 November 2025}}</ref> |- | Chalcedony || Almost any color || Varies by color || Fibrous form of silica composed mostly of quartz with some intergrown moganite (1-20%), occurs in many sub-varieties || Cryptocrystalline, microcrystalline || Transparent to opaque || Widespread || 150px Chalcedony from Czech Republic || <ref name="chalcedony" /> |- | Citrine || Natural: yellow to yellow-green or yellow-orange, often with smoky hues Heat-treated amethyst: yellow-orange, orange, red, brown || Natural: no scientific consensus (either aluminum color centers or trace iron impurities) Heat-treated amethyst: trace amounts of iron oxides (hematite and goethite) || Natural citrine is rare; most material sold as citrine is heat-treated amethyst or sometimes heat-treated smoky quartz. Quartz colored yellow from stains, coatings, or inclusions is generally not considered citrine. || Macrocrystalline || Transparent || Brazil || 150px Twinned natural citrine crystals from Russia 150px "Citrine" (heat-treated amethyst) geode|| <ref name="International Gem Society">{{Cite news |title=Citrine Value, Price, and Jewelry Information - International Gem Society |url=https://www.gemsociety.org/article/citrine-jewelry-gemstone-information/ |archive-url=https://web.archive.org/web/20250130115505/https://www.gemsociety.org/article/citrine-jewelry-gemstone-information/ |archive-date=2025-01-30 |access-date=2025-02-02 |work=International Gem Society |language=en-US |url-status=live }}</ref><ref name=":0">{{Cite web |title=Citrine |url=https://www.mindat.org/min-1054.html |access-date=2025-01-10 |website=www.mindat.org}}</ref><ref>{{Cite web |title=Burnt amethyst |url=https://www.mindat.org/min-40451.html |access-date=2025-09-15 |website=www.mindat.org}}</ref> |- | Cotterite || Silvery metallic sheen || Develops in very thin layers with extremely thin cracks that produce a light-scattering effect giving cotterite a pearly metallic luster || Extremely rare. Derived from a single vein of calcite, quartz and ferruginous mud in Carboniferous Limestone in Rockforest, County Cork, Ireland || Macrocrystalline || Opaque || Ireland || 150px|Cotterite - The World’s Rarest form of Quartz Cotterite from Ireland || <ref>{{cite web |title=Boy (7) strikes it lucky by finding one of the world’s rarest minerals near his home in Cork |url=https://www.irishtimes.com/environment/2026/01/10/boy-7-strikes-it-lucky-by-finding-one-of-the-worlds-rarest-minerals-near-his-home-in-cork/ |website=Irish Times |access-date=13 January 2026}}</ref><ref>{{cite web |title=Cotterite |url=https://www.mindat.org/min-9938.html |website=Mindat.org |access-date=13 January 2026}}</ref><ref name="Roycroft_2016">{{cite journal |title=Cotterite: Historical review; extant specimens; etymology of 'Cotterite' and the genealogy of 'Miss Cotter'; new observations on the Cotterite texture | last=Roycroft |first=P.D. |journal=Irish Journal of Earth Sciences |year=2016 |volume=34 |pages=45–78 |doi=10.3318/ijes.2016.34.45}}</ref> |- | Dumortierite quartz || Blue, shades of purple and gray || Mineral inclusions || Contains silky inclusions of blue dumortierite || Macrocrystalline || Translucent || || 150px Dumortierite quartz from Brazil || <ref name=gemstone>{{cite web | url=http://www.minerals.net/gemstone/dumortierite_gemstone.aspx | title=The Gemstone Dumortierite | publisher=Minerals.net | access-date=23 April 2017 | archive-url=https://web.archive.org/web/20170506074639/http://www.minerals.net/gemstone/dumortierite_gemstone.aspx | archive-date=6 May 2017 | url-status=live | df=dmy-all }}</ref><ref name=Cally>{{cite book|title=Firefly Guide to Gems|first=Cally|last=Oldershaw|publisher=Firefly Books|date=2003|isbn=9781552978146|url=https://archive.org/details/fireflyguidetoge0000olde|url-access=registration|pages=[https://archive.org/details/fireflyguidetoge0000olde/page/100 100]|access-date=19 February 2017}}</ref><ref>{{cite web |last1=Friedman |first1=Herschel |title=THE GEMSTONE DUMORTIERITE |url=https://www.minerals.net/gemstone/dumortierite_gemstone.aspx |website=Minerals.net |access-date=28 November 2020}}</ref> |- | Jasper || Typically red to brown; may have other colors || || Impure variety of chalcedony || Microcrystalline || Opaque || || 150px Red jasper from Japan || |- | Milky quartz || White || Minute fluid inclusions of gas, liquid, or both, trapped during crystal formation || Less desirable as a gemstone || Macrocrystalline || Translucent to opaque || || 150px Milky quartz from Colorado, USA || <ref>{{Cite book|url=https://books.google.com/books?id=KLSTDgAAQBAJ&pg=PA97|title=Gemstones: A Complete Color Reference for Precious and Semiprecious Stones of the World|last1=Hurrell|first1=Karen|last2=Johnson|first2=Mary L.|year=2016|publisher=Book Sales|isbn=978-0-7858-3498-4|page=97}}</ref><ref>[http://www.galleries.com/minerals/silicate/milky_qu/milky_qu.htm Milky quartz at Mineral Galleries] {{Webarchive|url=https://web.archive.org/web/20081219020818/http://www.galleries.com/minerals/silicate/milky_qu/milky_qu.htm |date=19 December 2008 }}. Galleries.com. Retrieved 2013-03-07.</ref> |- | Onyx || Black and white, monochromatic || Carbon impurities || Variety of agate || Cryptocrystalline, microcrystalline || Semi-translucent to opaque || || 150px Onyx from Germany || |- | {{anchor|Prase}}Prase || Leek green || Inclusions of the amphibole mineral actinolite || As originally defined in Germany. The name ''prase'' has also been used historically for similarly-colored quartzite and jasper, and today it may refer to any leek-green quartz. || Macrocrystalline || || || 150px Prase from Tuscany, Italy || <ref name="Klemme_etal_2018">{{cite journal | title=On the Color and Genesis of Prase (Green Quartz) and Amethyst from the Island of Serifos, Cyclades, Greece | first1=S. | last1=Klemme | first2=J. | last2=Berndt | first3=C. | last3=Mavrogonatos | first4=S. | last4=Flemetakis | first5=I. | last5=Baziotis | first6=P. | last6=Voudouris | first7=S. | last7=Xydous | journal=Minerals | date=2018 | volume=8 | issue=11 | page=487 | doi=10.3390/min8110487 | bibcode=2018Mine....8..487K | doi-access=free }}</ref><ref name=":3">{{Cite web |title=Prase |url=https://www.mindat.org/min-6703.html |access-date=2025-01-21 |website=www.mindat.org}}</ref> |- | Prasiolite (vermarine, green amethyst) || Green || Trace Fe2+ compounds || Rare. Most material sold as prasiolite is produced by heating amethyst. || Macrocrystalline || Transparent || Brazil; Thunder Bay, Canada; Poland || 150px Cut prasiolite from Brazil || <ref name=QtzPage>{{cite web |url=http://www.quartzpage.de/prasiolite.html |title=Prasiolite |publisher=quarzpage.de |date=28 October 2009 |access-date=28 November 2010 |archive-url=https://web.archive.org/web/20110713052049/http://www.quartzpage.de/prasiolite.html |archive-date=13 July 2011 |url-status=live }}</ref><ref>{{cite web |title=Prasiolite |url=https://www.mindat.org/min-40112.html |website=mindat.org |publisher=Hudson Institute of Mineralogy |access-date=27 December 2025}}</ref> |- | Rock crystal (clear quartz) || Colorless || Absence of impurities || || Macrocrystalline || Transparent to translucent || || 150px Clear quartz crystals || |- | Rose quartz || Pale pink to rose || Microscopic inclusions of a fibrous mineral related to dumortierite Euhedral rose quartz: aluminum and phosphorus color centers || Rose quartz is always massive and anhedral. However, a distinct variety called ''euhedral rose quartz'' or ''pink quartz'' occurs as well-formed hexagonal crystals. || Macrocrystalline || Translucent Euhedral rose quartz: transparent || || 150px Rose quartz 150px Euhedral rose quartz (pink quartz) cluster from Minas Gerais, Brazil || <ref>{{cite web |title=Rose Quartz |url=https://www.mindat.org/show.php?id=3456 |website=mindat.org |publisher=Hudson Institute of Mineralogy |access-date=7 December 2025}}</ref><ref>{{cite web |last1=Akhavan |first1=Amir C. |title=Rose Quartz |url=http://www.quartzpage.de/rose.html |website=The Quartz Page |access-date=7 December 2025}}</ref><ref>{{cite web |last1=Akhavan |first1=Amir C. |url=http://www.quartzpage.de/pink.html |title=Pink Quartz |website=The Quartz Page |access-date=7 December 2025}}</ref> |- | Rutilated quartz || Clear with golden-yellow or black inclusions || Mineral inclusions || Contains acicular (needle-like) inclusions of rutile|| Macrocrystalline || Transparent to translucent || || 150px Rutilated quartz cluster from Brazil || |- | Smoky quartz || Light to dark gray, brown, black || Color centers around aluminum impurities activated by natural irradiation || || Macrocrystalline || Translucent to opaque || || 150px Smoky quartz from Brazil || <ref>{{cite journal |last1=Fridrichová |first1=Jana |last2=Bačík |first2=Peter |last3=Illášová |first3=Ľudmila |last4=Kozáková |first4=Petra |last5=Škoda |first5=Radek |last6=Pulišová |first6=Zuzana |last7=Fiala |first7=Anton |title=Raman and optical spectroscopic investigation of gem-quality smoky quartz crystals |journal=Vibrational Spectroscopy |date=July 2016 |volume=85 |pages=71–78 |doi=10.1016/j.vibspec.2016.03.028|bibcode=2016VibSp..85...71F }}</ref> |- | Tiger's eye || Gold, red-brown, blue || || Exhibits chatoyancy || Macrocrystalline || Opaque || || 150px Rough tiger's eye 150px Polished red tiger's eye || |- |}

== Piezoelectricity == Quartz crystals have piezoelectric properties; they develop an electric potential upon the application of mechanical stress.<ref>{{cite book |author1-last=Saigusa |author1-first=Y. |year=2017 |chapter= Chapter 5 – Quartz-Based Piezoelectric Materials |editor1-last=Uchino |editor1-first=Kenji |title=Advanced Piezoelectric Materials |series=Woodhead Publishing in Materials |edition=2nd |publisher=Woodhead Publishing |pages=197–233 |doi=10.1016/B978-0-08-102135-4.00005-9 |isbn=9780081021354}}</ref> Quartz's piezoelectric properties were discovered by Jacques and Pierre Curie in 1880.<ref>{{cite journal|author=Curie, Jacques |author2=Curie, Pierre |year=1880|title=Développement par compression de l'électricité polaire dans les cristaux hémièdres à faces inclinées|trans-title=Development, via compression, of electric polarization in hemihedral crystals with inclined faces|journal=Bulletin de la Société minéralogique de France|volume= 3|issue=4 | pages =90–93|url=https://babel.hathitrust.org/cgi/pt?id=uc1.b3616891&view=1up&seq=100 |doi=10.3406/bulmi.1880.1564 |url-access=subscription}}. Reprinted in: {{cite journal |author=Curie, Jacques |author2=Curie, Pierre |year=1880 |title=Développement, par pression, de l'électricité polaire dans les cristaux hémièdres à faces inclinées |url=http://gallica.bnf.fr/ark:/12148/bpt6k30485/f296.image |journal=Comptes rendus |volume=91 |pages=294–295 |access-date=17 December 2013 |archive-url=https://web.archive.org/web/20121205083302/http://gallica.bnf.fr/ark:/12148/bpt6k30485/f296.image |archive-date=5 December 2012 |url-status=live }}</ref><ref>{{cite journal|author=Curie, Jacques|author2=Curie, Pierre|year=1880|title=Sur l'électricité polaire dans les cristaux hémièdres à faces inclinées|trans-title=On electric polarization in hemihedral crystals with inclined faces|url=http://gallica.bnf.fr/ark:/12148/bpt6k30485/f385.image|journal=Comptes rendus|volume=91|pages=383–386|access-date=17 December 2013|archive-url=https://web.archive.org/web/20121205090430/http://gallica.bnf.fr/ark:/12148/bpt6k30485/f385.image|archive-date=5 December 2012|url-status=live}}</ref>

== Occurrence == thumb|Quartz vein in sandstone, North Carolina Quartz is the second most abundant mineral or mineral group in the Earth's lithosphere; by mass, the feldspar group comprises 41% of the lithosphere, followed by quartz at 12% and the pyroxene group at 11%.<ref>{{cite book |first1=Robert S. |last1=Anderson |first2=Suzanne P. |last2=Anderson |title=Geomorphology: The Mechanics and Chemistry of Landscapes |publisher=Cambridge University Press |year=2010 |page=187|url=https://books.google.com/books?id=hDt5A2-km_wC|isbn=978-1-139-78870-0}}</ref> Quartz is a defining constituent of granite and other felsic igneous rocks. It is very common in sedimentary rocks such as sandstone and shale. It is a common constituent of schist, gneiss, quartzite and other metamorphic rocks.<ref name=Klein/> Quartz has the lowest potential for weathering in the Goldich dissolution series and consequently it is very common as a residual mineral in stream sediments and residual soils. Generally a high presence of quartz suggests a "mature" rock, since it indicates the rock has been heavily reworked and quartz was the primary mineral that endured heavy weathering.<ref>{{cite book |last1=Boggs |first1=Sam |title=Principles of sedimentology and stratigraphy |date=2006 |publisher=Pearson Prentice Hall |location=Upper Saddle River, N.J. |isbn=0131547283 |edition=4th |page=130}}</ref>

While the majority of quartz crystallizes from molten magma, quartz also chemically precipitates from hot hydrothermal veins as gangue, sometimes with ore minerals such as gold, silver and copper. Large crystals of quartz are found in magmatic pegmatites.<ref name=Klein/> Well-formed crystals may reach several meters in length and weigh hundreds of kilograms.<ref>{{cite journal|first1=Richard H. |last1=Jahns |title=The genesis of pegmatites: I. Occurrence and origin of giant crystals |journal=American Mineralogist |year=1953 |volume=38 |number=7–8 |pages=563–598 |url=https://pubs.geoscienceworld.org/msa/ammin/article-abstract/38/7-8/563/539244 |access-date=7 April 2021}}</ref>

The largest documented single crystal of quartz was found near Itapore, Goiaz, Brazil; it measured approximately {{convert|6.1|x|1.5|x|1.5|m|ft|0|abbr=on}} and weighed over {{cvt|88000|lb|kg|order=flip|sigfig=3}}.<ref>{{cite journal| url = http://www.minsocam.org/ammin/AM66/AM66_885.pdf| journal = American Mineralogist| volume = 66| pages = 885–907 (903)| year = 1981| title = The largest crystals| author = Rickwood, P. C.| access-date = 7 March 2013| archive-url = https://web.archive.org/web/20130825210420/http://www.minsocam.org/ammin/AM66/AM66_885.pdf| archive-date = 25 August 2013| url-status = live| df = dmy-all}}</ref>

== Mining == Quartz is extracted from open-pit mines. Miners occasionally use explosives to expose deep pockets of quartz. More frequently, bulldozers and backhoes are used to remove soil and clay and expose quartz veins, which are then worked using hand tools. Care must be taken to avoid sudden temperature changes that may damage the crystals.<ref>{{cite web |last1=McMillen |first1=Allen |title=Quartz Mining |url=https://encyclopediaofarkansas.net/entries/quartz-mining-1173/ |website=Encyclopedia of Arkansas |publisher=Central Arkansas Library System |access-date=28 November 2020}}</ref><ref>{{Cite web|url=https://sciencing.com/quartz-extracted-8700692.html|title=How Is Quartz Extracted?|website=sciencing.com|date=25 April 2017|author=Eleanor McKenzie|access-date=2020-01-28}}</ref>

== Related silica minerals == {{See also|Silica minerals}} thumb|right|upright=1.3|Pressure-temperature diagram showing the stability ranges for the two forms of quartz and some other forms of silica<ref>"Mineral Science" by Cornelis Klein; {{ISBN|0-471-25177-1}}</ref> Tridymite and cristobalite are high-temperature polymorphs of SiO2 that occur in high-silica volcanic rocks. Coesite is a denser polymorph of SiO2 found in some meteorite impact sites and in metamorphic rocks formed at pressures greater than those typical of the Earth's crust. Stishovite is a yet denser and higher-pressure polymorph of SiO2 found in some meteorite impact sites.{{r|Nesse|pp=201-202}} Moganite is a monoclinic polymorph. Lechatelierite is an amorphous silica glass SiO2 which is formed by lightning strikes in quartz sand.<ref>{{cite web |title=Lechatelierite |url=https://www.mindat.org/min-2363.html |website=Mindat.org |access-date=7 April 2021}}</ref>

== Safety == As quartz is a form of silica, it is a possible cause for concern in various workplaces. Cutting, grinding, chipping, sanding, drilling, and polishing natural and manufactured stone products can release hazardous levels of very small, crystalline silica dust particles into the air that workers breathe.<ref>{{cite book |title=Hazard Alert - Worker Exposure to Silica during Countertop Manufacturing, Finishing and Installation |publisher=DHHS (NIOSH) |page=2 |url=https://www.osha.gov/Publications/OSHA3768.pdf |access-date=27 November 2019}}</ref> Crystalline silica of respirable size is a recognized human carcinogen and may lead to other diseases of the lungs such as silicosis and pulmonary fibrosis.<ref>{{cite web |title=Silica (crystalline, respirable) |url=https://oehha.ca.gov/chemicals/silica-crystalline-respirable |website=OEHHA |publisher=California Office of Environmental Health Hazard Assessment |access-date=27 November 2019}}</ref><ref>{{cite book |title=Arsenic, Metals, Fibres and Dusts. A Review of Human Carcinogens |date=2012 |publisher=International Agency for Research on Cancer |isbn=978-92-832-1320-8 |pages=355–397 |edition=100C |url=https://www.ncbi.nlm.nih.gov/books/NBK304375/pdf/Bookshelf_NBK304375.pdf |access-date=27 November 2019}}</ref>

== 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 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 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>{{Cite news |last=Liccini |first=Mark |title=Treating Quartz to Create Color - International Gem Society IGS |url=http://www.gemsociety.org/article/treating-quartz-color/ |archive-url=https://web.archive.org/web/20141223233321/http://www.gemsociety.org/article/treating-quartz-color/ |archive-date=2014-12-23 |access-date=2026-03-01 |work=International Gem Society IGS |language=en-US}}</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 |issue=1 |pages=29–43 |doi=10.15506/JoG.2012.33.1.29 |bibcode=2012JGem...33...29H |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 twinned, synthetic quartz is produced for use in industry. Large, flawless single crystals are synthesized in an autoclave via the 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><ref name="Klein" /><ref>{{Cite web |date=2016-07-04 |title=san thach anh kobler |url=https://sankobler.com/ |access-date=2026-03-01 |website=sankobler.com |language=en}}</ref><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 coated with metal vapors to give it an attractive sheen.<ref>{{Cite book |last=O'Donoghue |first=Michael |url=https://books.google.com/books?id=ZwcM5H-wHNoC&q=%22%222aqua+aura%22%222+-healing&pg=PT28 |title=Gems: Their Sources, Descriptions and Identification |last2=Robert |first2=Webster |date=January 2006 |publisher=Butterworth-Heinemann |isbn=978-0-7506-5856-0 |language=en}}</ref><ref>{{Cite web |last=Team |first=Geology In |title=What is Aura Rainbow Quartz and How Is It Made? |url=https://www.geologyin.com/2017/06/how-is-aura-rainbow-quartz-made.html |access-date=2026-03-01 |website=Geology In |language=en}}</ref>

== Uses == Quartz is the most common material identified as the mystical substance maban in Australian Aboriginal mythology. It is found regularly in passage tomb cemeteries in Europe in a burial context, such as Newgrange or Carrowmore in Ireland. Quartz was also used in prehistoric Ireland, as well as many other countries, for stone tools; both vein quartz and rock crystal were knapped as part of the lithic technology of prehistoric peoples.<ref>{{Cite thesis |first=Killian |last=Driscoll |title=quartz lithic technology history quartz lithic research Ireland chapter 3 |date=2010 |degree=PhD |publisher=University College Dublin |url=http://www.lithicsireland.ie/phd_quartz_lithic_technology_chap_3.html |archive-url=https://web.archive.org/web/20170625005416/http://www.lithicsireland.ie/phd_quartz_lithic_technology_chap_3.html |archive-date=2017-06-25}}</ref>

While jade has been the most prized semi-precious stone for carving in East Asia and pre-Columbian America since earliest times, in Europe and the Middle East different varieties of quartz were the most commonly used for the various types of jewelry and hardstone carving, including engraved gems and cameo gems, rock crystal vases, and extravagant vessels. The tradition continued to produce highly valued objects until the mid-19th century, when it largely fell from fashion except in jewelry. Cameo technique exploits the bands of color in onyx and other varieties.

Efforts to synthesize quartz began in the mid-19th century as scientists attempted to create minerals under laboratory conditions that mimicked the conditions in which the minerals formed in nature. German geologist Karl Emil von Schafhäutl (1803–1890) was the first person to synthesize quartz when in 1845 he created microscopic quartz crystals in a pressure cooker.<ref>{{cite journal |first=Karl Emil |last=von Schafhäutl |title=Die neuesten geologischen Hypothesen und ihr Verhältniß zur Naturwissenschaft überhaupt (Fortsetzung) |trans-title=The latest geological hypotheses and their relation to science in general (continuation) |journal=Gelehrte Anzeigen |volume=20 |issue=72 |date=10 April 1845 |pages=577–584 |location=München |publisher=im Verlage der königlichen Akademie der Wissenschaften, in Commission der Franz'schen Buchhandlung |url=https://archive.org/stream/gelehrteanzeige06wissgoog#page/n298/mode/1up |oclc=1478717}} From page 578: 5) ''Bildeten sich aus Wasser, in welchen ich im Papinianischen Topfe frisch gefällte Kieselsäure aufgelöst hatte, beym Verdampfen schon nach 8 Tagen Krystalle, die zwar mikroscopisch, aber sehr wohl erkenntlich aus sechseitigen Prismen mit derselben gewöhnlichen Pyramide bestanden.'' ( 5) There formed from water in which I had dissolved freshly precipitated silicic acid in a Papin pot [i.e., pressure cooker], after just 8 days of evaporating, crystals, which albeit were microscopic but consisted of very easily recognizable six-sided prisms with their usual pyramids.)</ref> However, the quality and size of the crystals that were produced by these early efforts were poor.<ref>Byrappa, K. and Yoshimura, Masahiro (2001) ''Handbook of Hydrothermal Technology''. Norwich, New York: Noyes Publications. {{ISBN|008094681X}}. [https://books.google.com/books?id=-rYel1Q2HB8C&pg=PA53 Chapter 2: History of Hydrothermal Technology].</ref>

Elemental impurity incorporation strongly influences the ability to process and utilize quartz. Naturally occurring quartz crystals of extremely high purity, necessary for the crucibles and other equipment used for growing perfect large silicon boules to be sliced into silicon wafers in the semiconductor industry, are expensive and rare. These high-purity quartz are defined as containing less than 50 ppm of impurity elements.<ref>{{Cite journal |last1=Götze |first1=Jens |last2=Pan |first2=Yuanming |last3=Müller |first3=Axel |date=October 2021 |title=Mineralogy and mineral chemistry of quartz: A review |journal=Mineralogical Magazine |language=en |volume=85 |issue=5 |pages=639–664 |doi=10.1180/mgm.2021.72 |bibcode=2021MinM...85..639G |s2cid=243849577 |issn=0026-461X|doi-access=free }}</ref> A major mining location for high-purity quartz is the Spruce Pine Mining District in Spruce Pine, North Carolina, United States.<ref>{{cite news|url=http://news.bbc.co.uk/2/hi/technology/8178580.stm|author=Nelson, Sue|title=Silicon Valley's secret recipe|work=BBC News|date=2009-08-02|access-date=16 September 2009|archive-url=https://web.archive.org/web/20090805092039/http://news.bbc.co.uk/2/hi/technology/8178580.stm|archive-date=5 August 2009|url-status=live}}</ref> Quartz may also be found in Caldoveiro Peak in Asturias, Spain.<ref>{{Cite web |title=Caldoveiro Mine, Tameza, Asturias, Spain |url=https://www.mindat.org/loc-122679.html |archive-url=https://web.archive.org/web/20180212083356/https://www.mindat.org/loc-122679.html |archive-date=2018-02-12 |access-date=2026-03-01 |website=www.mindat.org}}</ref>

By the 1930s, the electronics industry had become dependent on quartz crystals. The only source of suitable crystals was Brazil; however, World War II disrupted supplies from Brazil, so nations attempted to synthesize quartz on a commercial scale. German mineralogist Richard Nacken (1884–1971) achieved some success during the 1930s and 1940s.<ref>Nacken, R. (1950) "Hydrothermal Synthese als Grundlage für Züchtung von Quarz-Kristallen" (Hydrothermal synthesis as a basis for the production of quartz crystals), ''Chemiker Zeitung'', '''74''' : 745–749.</ref> After the war, many laboratories attempted to grow large quartz crystals. In the United States, the U.S. Army Signal Corps contracted with Bell Laboratories and with the Brush Development Company of Cleveland, Ohio to synthesize crystals following Nacken's lead.<ref>{{Cite journal | doi = 10.1126/science.107.2781.393| pmid = 17783928| title = The Laboratory Growing of Quartz| journal = Science| volume = 107| issue = 2781| pages = 393–394| year = 1948| last1 = Hale | first1 = D. R.| bibcode = 1948Sci...107..393H}}</ref><ref>{{Cite journal| doi = 10.1109/MIM.2011.6041381| url = http://tf.nist.gov/general/pdf/2534.pdf| title = The evolution of time measurement, Part 2: Quartz clocks [Recalibration]| journal = IEEE Instrumentation & Measurement Magazine| volume = 14| issue = 5| pages = 41–48| year = 2011| last1 = Lombardi| first1 = M.| s2cid = 32582517| access-date = 30 March 2013| archive-url = https://web.archive.org/web/20130527002612/http://tf.nist.gov/general/pdf/2534.pdf| archive-date = 27 May 2013| url-status = live| df = dmy-all}}</ref> (Prior to World War II, Brush Development produced piezoelectric crystals for record players.) By 1948, Brush Development had grown crystals that were 1.5 inches (3.8 cm) in diameter, the largest at that time.<ref>[https://books.google.com/books?id=pCQDAAAAMBAJ&pg=PA148 "Record crystal"], ''Popular Science'', '''154''' (2) : 148 (February 1949).</ref><ref>Brush Development's team of scientists included: Danforth R. Hale, Andrew R. Sobek, and Charles Baldwin Sawyer (1895–1964). The company's U.S. patents included: * Sobek, Andrew R. "Apparatus for growing single crystals of quartz", {{US Patent|2674520}}; filed: 11 April 1950; issued: 6 April 1954. * Sobek, Andrew R. and Hale, Danforth R. "Method and apparatus for growing single crystals of quartz", {{US Patent|2675303}}; filed: 11 April 1950; issued: 13 April 1954. * Sawyer, Charles B. "Production of artificial crystals", {{US Patent|3013867}}; filed: 27 March 1959; issued: 19 December 1961. (This patent was assigned to Sawyer Research Products of Eastlake, Ohio.)</ref> By the 1950s, hydrothermal synthesis techniques were producing synthetic quartz crystals on an industrial scale, and today virtually all the quartz crystal used in the modern electronics industry is synthetic.<ref name="buisson-arnaud-1994"/>

An early use of the piezoelectricity of quartz crystals was in phonograph pickups. One of the most common piezoelectric uses of quartz today is as a crystal oscillator. Also called a quartz oscillator or resonator, it was first developed by Walter Guyton Cady in 1921.<ref>{{cite journal|author=Cady, W. G. |year=1921|title=The piezoelectric resonator|journal=Physical Review |volume=17|pages=531–533|doi=10.1103/PhysRev.17.508|url=https://zenodo.org/record/2523161}}</ref><ref>{{cite web|url=http://invention.smithsonian.org/centerpieces/quartz/inventors/cady.html |title=The Quartz Watch – Walter Guyton Cady |publisher=The Lemelson Center, National Museum of American History, Smithsonian Institution |url-status=dead |archive-url=https://web.archive.org/web/20090104143758/http://invention.smithsonian.org/centerpieces/quartz/inventors/cady.html |archive-date=4 January 2009 }}</ref> George Washington Pierce designed and patented quartz crystal oscillators in 1923.<ref>{{cite journal|jstor=20026061|author=Pierce, G. W. |year=1923|title=Piezoelectric crystal resonators and crystal oscillators applied to the precision calibration of wavemeters|journal=Proceedings of the American Academy of Arts and Sciences|volume=59|issue=4|pages=81–106|doi=10.2307/20026061|hdl=2027/inu.30000089308260 |hdl-access=free}}</ref><ref>Pierce, George W. "Electrical system", {{US Patent|2133642}}, filed: 25 February 1924; issued: 18 October 1938.</ref><ref>{{cite web|url=http://invention.smithsonian.org/centerpieces/quartz/inventors/pierce.html |title=The Quartz Watch – George Washington Pierce |publisher=The Lemelson Center, National Museum of American History, Smithsonian Institution |url-status=dead |archive-url=https://web.archive.org/web/20090104145422/http://invention.smithsonian.org/centerpieces/quartz/inventors/pierce.html |archive-date=4 January 2009 }}</ref> The quartz clock is a familiar device using the mineral; it is simply a clock that uses a quartz oscillator as its time reference. Warren Marrison created the first quartz oscillator clock based on the work of Cady and Pierce in 1927.<ref>{{cite web|url=http://invention.smithsonian.org/centerpieces/quartz/inventors/clock.html |title=The Quartz Watch – Warren Marrison |publisher=The Lemelson Center, National Museum of American History, Smithsonian Institution |url-status=dead |archive-url=https://web.archive.org/web/20090125110103/http://invention.smithsonian.org/centerpieces/quartz/inventors/clock.html |archive-date=25 January 2009 }}</ref> The resonant frequency of a quartz crystal oscillator is changed by mechanically loading it, and this principle is used for very accurate measurements of very small mass changes in the quartz crystal microbalance and in thin-film thickness monitors.<ref name="Sauerbrey_1959">{{Cite journal |author-last=Sauerbrey |author-first=Günter Hans |author-link=Günter Sauerbrey |title=Verwendung von Schwingquarzen zur Wägung dünner Schichten und zur Mikrowägung |language=de |doi=10.1007/BF01337937 |journal=Zeitschrift für Physik |publisher=Springer-Verlag |volume=155 |issue=2 |pages=206–222 |date=April 1959 |orig-year=1959-02-21 |issn=0044-3328 |bibcode=1959ZPhy..155..206S |s2cid=122855173 |url=http://jmfriedt.sequanux.org/t/sauerbrey.pdf |access-date=2019-02-26 |url-status=live |archive-url=https://web.archive.org/web/20190226103453/http://jmfriedt.sequanux.org/t/sauerbrey.pdf |archive-date=2019-02-26}} (NB. This was partially presented at Physikertagung in Heidelberg in October 1957.)</ref>

<gallery class="center" widths=200 heights=250> File:Milan Jug with cut festoon decoration.jpg|Rock crystal jug with cut festoon decoration by a Milan workshop from the second half of the 16th century, National Museum, Warsaw. Milan, apart from Prague and Florence, was the main Renaissance centre for crystal cutting.<ref>{{cite book |title=The International Antiques Yearbook |year=1972 |page=78 |publisher=Studio Vista Limited |url=https://books.google.com/books?id=BVcvAQAAIAAJ|quote=Apart from Prague and Florence, the main Renaissance centre for crystal cutting was Milan.}}</ref> File:Prototype synthetic quartz autoclave 1959.jpg|Synthetic quartz crystals produced in the autoclave shown in Western Electric's pilot hydrothermal quartz plant in 1959 File:Ewer birds Louvre MR333.jpg|Fatimid ewer in carved rock crystal (clear quartz) with gold lid, {{Circa|1000}} </gallery>

Almost all the industrial demand for quartz crystal (used primarily in electronics) is met with synthetic quartz produced by the hydrothermal process. However, synthetic crystals are less prized for use as gemstones.<ref>{{cite web |title=Hydrothermal Quartz |url=https://www.gemselect.com/other-info/synthetic-quartz.php |website=Gem Select |publisher=GemSelect.com |access-date=28 November 2020}}</ref> The popularity of crystal healing has increased the demand for natural quartz crystals, which are now often mined in developing countries using primitive mining methods, sometimes involving child labor.<ref>{{Cite news|url=https://www.theguardian.com/lifeandstyle/2019/sep/17/healing-crystals-wellness-mining-madagascar|title=Dark crystals: the brutal reality behind a booming wellness craze|last=McClure|first=Tess|date=2019-09-17|work=The Guardian|access-date=2019-09-25|language=en-GB|issn=0261-3077}}</ref>

== See also == {{Portal|Minerals|Geology|Earth sciences}} * Fused quartz * List of minerals * Quartz fiber * Quartz reef mining * Quartzolite * Shocked quartz

== References == {{Reflist}}

== External links == {{Commons category|Quartz}} {{Wiktionary|quartz}} {{Wikisource|1911_Encyclopædia_Britannica/Quartz|EB1911:Quartz}} * [https://web.archive.org/web/20140119002111/http://www.lixinsurface.com/ Quartz varieties, properties, crystal morphology. Photos and illustrations] * [https://web.archive.org/web/20071120041430/http://www.minsocam.org/msa/collectors_corner/arc/silicanom.htm Gilbert Hart, "Nomenclature of Silica", ''American Mineralogist'', Volume 12, pp. 383–395. 1927] * {{cite web|url=http://invention.smithsonian.org/centerpieces/quartz/inventors/index.html |title=The Quartz Watch – Inventors |publisher=The Lemelson Center, National Museum of American History, Smithsonian Institution |url-status=dead |archive-url=https://web.archive.org/web/20090107020810/http://invention.smithsonian.org/centerpieces/Quartz/inventors/index.html |archive-date=7 January 2009 }} * [https://web.archive.org/web/20071012101816/http://www.connogue.com/quartslab/html/terminology.html Terminology used to describe the characteristics of quartz crystals when used as oscillators] * [http://www.lithicsireland.ie/phd_quartz_lithic_technology_chap_1.html Quartz use as prehistoric stone tool raw material]

Category:Quartz Category:Dielectrics Category:Piezoelectric materials Category:Symbols of Georgia (U.S. state) Category:Trigonal minerals Category:Minerals in space group 152 or 154 Category:Minerals in space group 180 or 181 Category:Luminescent minerals Quartz gemstones Category:Industrial minerals Category:Silica polymorphs Category:Symbols of South Dakota