Quartz#Mining

The word "quartz" is derived from the German word {{Lang|de|Quarz}},{{cite web | url=https://www.merriam-webster.com/dictionary/quartz | title=Quartz | work=Merriam-Webster.com Dictionary | access-date=9 January 2024}} which had the same form in the first half of the 14th century in Middle High German and in East Central German[https://www.dwds.de/wb/Quarz Digitales Wörterbuch der deutschen Sprache] {{Webarchive|url=https://web.archive.org/web/20171201042329/https://www.dwds.de/wb/Quarz |date=1 December 2017 }} (in German) and which came from the Polish dialect term {{Lang|pl|twardy}}, which corresponds to the Czech term {{Lang|cs|tvrdý}} ("hard").{{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 }} Some sources, however, attribute the word's origin to the Saxon word Querkluftertz, meaning cross-vein ore.{{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.{{cite journal | title=On the origin of the name 'quartz' | last=Tomkeieff | first=S.I. | journal=Mineralogical Magazine | date=1942 | volume=26 | issue=176 | pages=172–178| doi=10.1180/minmag.1942.026.176.04 | bibcode=1942MinM...26..172T }}

The Ancient Greeks referred to quartz as {{Lang|grc|κρύσταλλος}} ({{Transliteration|grc|krustallos}}) derived from the Ancient Greek {{Lang|grc|κρύος}} ({{Transliteration|grc|kruos}}) meaning "icy cold", because some philosophers (including Theophrastus) understood the mineral to be a form of supercooled ice.{{cite journal | url=http://www.minersoc.org/pages/Archive-MM/Volume_26/26-176-172.pdf | title=On the origin of the name 'quartz' | author=Tomkeieff, S.I. | journal=Mineralogical Magazine | year=1942 | volume=26 | issue=176 | pages=172–178 | doi=10.1180/minmag.1942.026.176.04 | access-date=12 August 2015 | 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 | url-status=live | df=dmy-all | bibcode=1942MinM...26..172T }} Today, the term rock crystal is sometimes used as an alternative name for transparent coarsely crystalline quartz.{{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 }}{{cite book |last1=Nesse |first1=William D. |title=Introduction to mineralogy |date=2000 |publisher=Oxford University Press |location=New York |isbn=9780195106916 |page=205}}

Roman naturalist Pliny the Elder believed quartz to be water ice, permanently frozen after great lengths of time.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 }}. He supported this idea by saying that quartz is found near glaciers in the Alps, but not on volcanic mountains, and that large quartz crystals were fashioned into spheres to cool the hands. This idea persisted until at least the 17th century. He also knew of the ability of quartz to split light into a spectrum.{{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}}

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 joined at a perfect 60° angle, thus discovering the law of constancy of interfacial angles.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; … "

{{multiple image

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|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 belongs to the trigonal crystal system at room temperature, and to the hexagonal crystal system above {{convert|573|C|K F}}. The former is called α-quartz; the latter is β-quartz. The ideal crystal shape 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.{{sfn|Hurlbut|Klein|1985}}{{sfn|Nesse|2000|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.{{cite book |last1=Sinkankas |first1=John |title=Mineralogy for amateurs. |date=1964 |publisher=Van Nostrand |location=Princeton, N.J. |isbn=0442276249 |pages=443–447}} 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.{{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}}

α-quartz crystallizes in the trigonal crystal system, space group P3₁21 or P3₂21 (space group 152 or 154 resp.) depending on the chirality. Above {{convert|573|C|K F}}, α-quartz in P3₁21 becomes the more symmetric hexagonal P6₄22 (space group 181), and α-quartz in P3₂21 goes to space group P6₂22 (no. 180).Crystal Data, Determinative Tables, ACA Monograph No. 5, American Crystallographic Association, 1963

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.{{sfn|Hurlbut|Klein|1985}}{{sfn|Nesse|2000|p=201}} However, there is a significant change in volume during this transition,{{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? |url=https://www.sciencedirect.com/science/article/abs/pii/S0012821X20305665 |journal=Earth and Planetary Science Letters |volume=553 |pages=116622 |doi=10.1016/j.epsl.2020.116622 |bibcode=2021E&PSL.55316622J |issn=0012-821X}} and this can result in significant microfracturing in ceramics during firing,{{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}} in ornamental stone after a fire{{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 |pages=102823 |doi=10.1016/j.jobe.2021.102823 |issn=2352-7102|hdl=10045/115630 |hdl-access=free }} and in rocks of the Earth's crust exposed to high temperatures,{{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 |pages=116622 |doi=10.1016/j.epsl.2020.116622|bibcode=2021E&PSL.55316622J |s2cid=225116168 |doi-access=free }} thereby damaging materials containing quartz and degrading their physical and mechanical properties.

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

Although many of the varietal names historically arose from the color of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Color is a secondary identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties.{{Cite web|url=https://www.gemselect.com/gem-info/quartz/quartz-info.php|title=Quartz Gemstone and Jewelry Information: Natural Quartz – GemSelect|website=www.gemselect.com|access-date=2017-08-29|archive-url=https://web.archive.org/web/20170829171847/https://www.gemselect.com/gem-info/quartz/quartz-info.php|archive-date=29 August 2017|url-status=live}}

The most important microstructure difference between types of quartz is that of macrocrystalline quartz (individual crystals visible to the unaided eye) and the microcrystalline or cryptocrystalline varieties (aggregates of crystals visible only under high magnification). The cryptocrystalline varieties are either translucent or mostly opaque, while the macrocrystalline varieties tend to be more transparent. Chalcedony is a cryptocrystalline form of silica consisting of fine intergrowths of both quartz, and its monoclinic polymorph moganite.{{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}} Agate is a variety of chalcedony that is fibrous and distinctly banded with either concentric or horizontal bands.{{Cite web |title=Agate |url=https://www.mindat.org/min-51.html |access-date=2025-01-21 |website=www.mindat.org}} While most agates are translucent, onyx is a variety of agate that is more opaque, featuring monochromatic bands that are typically black and white.{{Cite web |title=Onyx |url=https://www.mindat.org/min-2999.html |access-date=2025-01-21 |website=www.mindat.org}} Carnelian or sard is a red-orange, translucent variety of chalcedony. Jasper is an opaque chert or impure chalcedony.{{Cite web |title=Jasper |url=https://www.mindat.org/min-2082.html |access-date=2025-01-21 |website=www.mindat.org}}

File:Transparency.jpg]]

Pure quartz, traditionally called rock crystal or clear quartz, is colorless and transparent or translucent and has often been used for hardstone carvings, such as the Lothair Crystal. Common colored varieties include citrine, rose quartz, amethyst, smoky quartz, milky quartz, and others.{{Cite web|url=http://www.minerals.net/gemstone/quartz_gemstone.aspx|title=Quartz: The gemstone Quartz information and pictures|website=www.minerals.net|language=en-US|access-date=2017-08-29|archive-url=https://web.archive.org/web/20170827194835/http://www.minerals.net/gemstone/quartz_gemstone.aspx|archive-date=27 August 2017|url-status=live}} 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 causing colors.

{{multiple image

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| image1 = Pure Quartz at Senckenberg Natural History Museum.jpg

| caption1 = Rock crystal

| image2 = Amethyst Siberia MNHN Minéralogie.jpg

| caption2 = Amethyst

| image3 = Shattuckite-Quartz-120842.jpg

| caption3 = Blue quartz

| image4 = Dumortierite-quartz (Brazil) 10.jpg

| caption4 = Dumortierite quartz

| image5 = Citrine 1 (Russie).jpg

| caption5 = Citrine quartz (natural)

| image6 = Citrine Macro - Large Vug.jpg

| caption6 = Citrine quartz (heat-altered amethyst)

| image7 = Quartz-221141.jpg

| caption7 = Milky quartz

| image8 = Quartz-194084.jpg

| caption8 = Rose quartz

| image9 = Quartz fumé 2(Brésil).jpg

| caption9 = Smoky quartz

| image10 = QuartzPrase.jpg

| caption10 = Prase

}}

Amethyst is a form of quartz that ranges from a bright vivid violet to a dark or dull lavender shade. The world's largest deposits of amethysts can be found in Brazil, Mexico, Uruguay, Russia, France, Namibia, and Morocco. Amethyst derives its color from traces of iron in its structure.{{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 }}

Ametrine, as its name suggests, is commonly believed to be a combination of citrine and amethyst in the same crystal; however, this may not be technically correct. Like amethyst, the yellow quartz component of ametrine is colored by iron oxide inclusions. Some, but not all, sources define citrine solely as quartz with its color originating from aluminum-based color centers.{{Cite web |title=Ametrine |url=https://www.mindat.org/min-7606.html |access-date=2025-01-10 |website=www.mindat.org}} Other sources do not make this distinction.{{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}} In the former case, the yellow quartz in ametrine is not considered true citrine. Regardless, most ametrine on the market is in fact partially heat- or radiation-treated amethyst.

Blue quartz contains inclusions of fibrous magnesio-riebeckite or crocidolite.{{cite web|title=Blue Quartz|publisher=Mindat.org|url=https://www.mindat.org/min-26723.html|access-date=24 February 2017|archive-url=https://web.archive.org/web/20170224211828/https://www.mindat.org/min-26723.html|archive-date=24 February 2017|url-status=live}}

Inclusions of the mineral dumortierite within quartz pieces often result in silky-appearing splotches with a blue hue. Shades of purple or gray sometimes also are present. "Dumortierite quartz" (sometimes called "blue quartz") will sometimes feature contrasting light and dark color zones across the material.{{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 }} "Blue quartz" is a minor gemstone.{{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}}{{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}}

Citrine is a variety of quartz whose color ranges from yellow to yellow-orange or yellow-green. The cause of its color is not well agreed upon. Evidence suggests the color of citrine is linked to the presence of aluminum-based color centers in its crystal structure, similar to those of smoky quartz. Both smoky quartz and citrine are dichroic in polarized light and will fade when heated sufficiently or exposed to UV light. They may occur together in the same crystal as “smoky citrine.” Smoky quartz can also be converted to citrine by careful heat treatment. Alternatively, it has been suggested that the color of citrine may be due to trace amounts of iron, but synthetic crystals grown in iron-rich solutions have failed to replicate the color or dichroism of natural citrine. The UV-sensitivity of natural citrine further indicates that its color is not caused solely by trace elements.{{Cite web |title=Citrine |url=https://www.mindat.org/min-1054.html |access-date=2025-01-10 |website=www.mindat.org}}

Natural citrine is rare; most commercial citrine is heat-treated amethyst or smoky quartz. Amethyst loses its natural violet color when heated to above 200-300°C and turns a color that resembles natural citrine, but is often more brownish.{{Cite web |title=Amethyst |url=https://www.mindat.org/min-198.html |access-date=2025-01-10 |website=www.mindat.org}} Unlike natural citrine, the color of heat-treated amethyst comes from trace amounts of the iron oxide minerals hematite and goethite. Clear quartz with natural iron inclusions or limonite staining may also resemble citrine, but it is not true citrine. Like amethyst, heat-treated amethyst often exhibits color zoning, or uneven color distribution throughout the crystal. In geodes and clusters, the color is usually deepest near the tips. This does not occur in natural citrine.

It is nearly impossible to differentiate between cut citrine and yellow topaz visually, but they differ in hardness. Brazil is the leading producer of citrine, with much of its production coming from the state of Rio Grande do Sul. The name is derived from the Latin word citrina which means "yellow" and is also the origin of the word "citron".[http://www.mindat.org/min-1054.html Citrine] {{Webarchive|url=https://web.archive.org/web/20100502064111/http://www.mindat.org/min-1054.html |date=2 May 2010 }}. Mindat.org (2013-03-01). Retrieved 2013-03-07. Citrine has been referred to as the "merchant's stone" or "money stone", due to a superstition that it would bring prosperity.{{cite encyclopedia |encyclopedia=The Encyclopedia of Superstitions |first = Richard|last = Webster|date = 8 September 2012 |url = https://books.google.com/books?id=m1-xCL47_7QC&q=citrine&pg=PA59|entry = Citrine |page = 59|isbn = 9780738725611}}

Citrine was first appreciated as a golden-yellow gemstone in Greece between 300 and 150 BC, during the Hellenistic Age. Yellow quartz was used prior to that to decorate jewelry and tools but it was not highly sought after.{{Cite web |url=http://thehealingchest.com/crystals-stones/citrine-meaning/ |title=Citrine Meaning |date=7 January 2016 |access-date=18 August 2017 |archive-url=https://web.archive.org/web/20170818175635/http://thehealingchest.com/crystals-stones/citrine-meaning/ |archive-date=18 August 2017 |url-status=live }}

Milk quartz or milky quartz is the most common variety of crystalline quartz. The white color is caused by minute fluid inclusions of gas, liquid, or both, trapped during crystal formation,{{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}} making it of little value for optical and quality gemstone applications.[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.

{{redirect|Rose Quartz|other uses}}

Rose quartz is a type of quartz that exhibits a pale pink to rose red hue. The color is usually considered as due to trace amounts of titanium, iron, or manganese in the material. Some rose quartz contains microscopic rutile needles that produce asterism in transmitted light. Recent X-ray diffraction studies suggest that the color is due to thin microscopic fibers of possibly dumortierite within the quartz.{{cite web |url=http://www.mindat.org/show.php?id=3456 |title=Rose Quartz |archive-url=https://web.archive.org/web/20090401031656/http://www.mindat.org/show.php?id=3456 |archive-date=1 April 2009 |website=Mindat.org |url-status=live |access-date=11 May 2023}}

Additionally, there is a rare type of pink quartz (also frequently called crystalline rose quartz) with color that is thought to be caused by trace amounts of phosphate or aluminium. The color in crystals is apparently photosensitive and subject to fading. The first crystals were found in a pegmatite found near Rumford, Maine, US, and in Minas Gerais, Brazil.{{cite web |url=http://minerals.caltech.edu/ge114/Lecture_Topics/Quartz/Index.htm |url-status=dead |title=Quartz and its colored varieties |archive-url=https://web.archive.org/web/20110719160220/http://minerals.caltech.edu/ge114/Lecture_Topics/Quartz/Index.htm |archive-date=19 July 2011 |publisher=California Institute of Technology}} The crystals found are more transparent and euhedral, due to the impurities of phosphate and aluminium that formed crystalline rose quartz, unlike the iron and microscopic dumortierite fibers that formed rose quartz.{{cite web |url=http://www.quartzpage.de/pink.html |title=Pink Quartz |website=The Quartz Page |access-date=11 May 2023}}

Smoky quartz is a gray, translucent version of quartz. It ranges in clarity from almost complete transparency to a brownish-gray crystal that is almost opaque. Some can also be black. The translucency results from natural irradiation acting on minute traces of aluminum in the crystal structure.{{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}}

Prase is a leek-green variety of quartz that gets its color from inclusions of the amphibole actinolite.{{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 }}{{Cite web |title=Prase |url=https://www.mindat.org/min-6703.html |access-date=2025-01-21 |website=www.mindat.org}} However, the term has also variously been used for a type of quartzite, a microcrystalline variety of quartz or jasper, or any leek-green quartz.

{{distinguish|Praseolite}}

Prasiolite, also known as vermarine, is a variety of quartz that is green in color.{{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 }} The green is caused by iron ions. It is a rare mineral in nature and is typically found with amethyst; most "prasiolite" is not natural – it has been artificially produced by heating of amethyst. {{citation needed span|text=Since 1950|date=April 2023}}, almost all natural prasiolite has come from a small Brazilian mine, but it is also seen in Lower Silesia in Poland. Naturally occurring prasiolite is also found in the Thunder Bay area of Canada.

Quartz crystals have piezoelectric properties; they develop an electric potential upon the application of mechanical stress.{{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}} Quartz's piezoelectric properties were discovered by Jacques and Pierre Curie in 1880.{{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 }}. 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 }}{{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}}

File:Quartz vein in sandstone (Thunderhead Sandstone, Neoproterozoic; Clingmans Dome, Great Smoky Mountains, North Carolina, USA) 2 (36619574200).jpg

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.{{sfn|Hurlbut|Klein|1985}} 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.{{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}}

While the majority of quartz crystallizes from molten magma, quartz also chemically precipitates from hot hydrothermal veins as gangue, sometimes with ore minerals like gold, silver and copper. Large crystals of quartz are found in magmatic pegmatites.{{sfn|Hurlbut|Klein|1985}} Well-formed crystals may reach several meters in length and weigh hundreds of kilograms.{{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}}

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}}.{{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}}

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.{{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}}{{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}}

{{See also|Silica minerals}}

File:P-T Diagram for SiO2.svg

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.{{sfn|Nesse|2000|pp=201-202}} Moganite is a monoclinic polymorph. Lechatelierite is an amorphous silica glass SiO₂ which is formed by lightning strikes in quartz sand.{{cite web |title=Lechatelierite |url=https://www.mindat.org/min-2363.html |website=Mindat.org |access-date=7 April 2021}}

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.{{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}} 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.{{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}}{{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}}

File:Quartz synthese (cropped).jpg, 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.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

Prasiolite, an olive colored material, is produced by heat treatment;{{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}} natural prasiolite has also been observed in Lower Silesia in Poland.{{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 }} Although citrine occurs naturally, the majority is the result of heat-treating amethyst or smoky quartz. Carnelian has been heat-treated to deepen its color since prehistoric times.{{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 }}

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.{{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}}{{sfn|Hurlbut|Klein|1985}}{{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 }}

Like other crystals, quartz may be coated with metal vapors to give it an attractive sheen.{{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 }}{{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}}

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 the prehistoric peoples.{{Cite web |url=http://www.lithicsireland.ie/phd_quartz_lithic_technology_chap_3.html |title=Driscoll, Killian. 2010. Understanding quartz technology in early prehistoric Ireland |access-date=19 July 2017 |archive-url=https://web.archive.org/web/20170625005416/http://www.lithicsireland.ie/phd_quartz_lithic_technology_chap_3.html |archive-date=25 June 2017 |url-status=live }}

While jade has been since earliest times the most prized semi-precious stone for carving in East Asia and Pre-Columbian America, in Europe and the Middle East the 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 objects that were very highly valued 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-nineteenth 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.{{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.) However, the quality and size of the crystals that were produced by these early efforts were poor.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].

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 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.{{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 }} A major mining location for high purity quartz is the Spruce Pine Gem Mine in Spruce Pine, North Carolina, United States.{{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}} Quartz may also be found in Caldoveiro Peak, in Asturias, Spain.{{cite web

|title = Caldoveiro Mine, Tameza, Asturias, Spain

|publisher = mindat.org

|url = https://www.mindat.org/loc-122679.html

|access-date = 15 February 2018

|archive-url = https://web.archive.org/web/20180212083356/https://www.mindat.org/loc-122679.html

|archive-date = 12 February 2018

|url-status = live

|df = dmy-all

}}

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 the 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.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. 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.{{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}}{{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}} (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.[https://books.google.com/books?id=pCQDAAAAMBAJ&pg=PA148 "Record crystal"], Popular Science, 154 (2) : 148 (February 1949).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.) 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.

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. The quartz oscillator or resonator was first developed by Walter Guyton Cady in 1921.{{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}}{{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 }} George Washington Pierce designed and patented quartz crystal oscillators in 1923.{{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}}Pierce, George W. "Electrical system", {{US Patent|2133642}}, filed: 25 February 1924; issued: 18 October 1938.{{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 }} The quartz clock is a familiar device using the mineral. Warren Marrison created the first quartz oscillator clock based on the work of Cady and Pierce in 1927.{{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 }} 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.{{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.)

File:Milan Jug with cut festoon decoration.jpg|Rock crystal jug with cut festoon decoration by Milan workshop from the second half of the 16th century, National Museum in Warsaw. The city of Milan, apart from Prague and Florence, was the main Renaissance centre for crystal cutting.{{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.}}

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}}

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.{{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}} 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.{{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}}

{{Portal|Minerals|Geology|Earth sciences}}

• Fused quartz
• List of minerals
• Quartz fiber
• Quartz reef mining
• Quartzolite
• Shocked quartz

{{Reflist}}

{{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]

{{Mohs}}{{Silica minerals}}{{Authority control}}

Category:Dielectrics

Category:Piezoelectric materials

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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

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