Editing Quartz (section)

{{short description|Mineral made of silicon and oxygen}}
{{About|the mineral|}}
{{Use American English|date=October 2021}}
{{Use dmy dates|date=June 2019}}
{{Infobox mineral
| name       = Quartz
| category   = [[Tectosilicates]], quartz [[Mineral group|group]]
| image = Quartz Brésil.jpg
| imagesize   =
| caption     = Quartz [[crystal cluster]] from [[Brazil]]
| formula     = SiO<sub>2</sub>
| 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 ([[oxide minerals|oxides]])
| dana = 75.01.03.01 ([[tectosilicate]]s)
| system = α-quartz: [[Trigonal crystal system|trigonal]] <br />β-quartz: [[Hexagonal crystal system|hexagonal]]
| class  = α-quartz: trapezohedral (class 3 2) <br />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: ''P3<sub>2</sub>21'' (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><br/>β-quartz: ''P6<sub>2</sub>22'' (no. 180) or ''P6<sub>4</sub>22'' (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 [[angstrom|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&nbsp;– lower in impure varieties (defining mineral)
| luster = Vitreous&nbsp;– waxy to dull when massive
| refractive = n<sub>ω</sub> = 1.543–1.545 <br />n<sub>ε</sub> = 1.552–1.554
| opticalprop = [[Uniaxial crystal|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&nbsp;°C (β [[tridymite]]); 1713&nbsp;°C (β [[cristobalite]])<ref name=Deer/>
| fusibility =
| diagnostic =
| solubility = Insoluble at [[standard conditions for temperature and pressure|STP]]; 1&nbsp;ppm<sub>mass</sub> at 400&nbsp;°C and 500&nbsp; lb/in<sup>2</sup> to 2600&nbsp;ppm<sub>mass</sub> at 500&nbsp;°C and 1500&nbsp;lb/in<sup>2</sup><ref name=Deer/>
| diaphaneity = Transparent to nearly opaque
| other = Lattice: [[hexagonal lattice system|hexagonal]], [[piezoelectricity|piezoelectric]], may be [[triboluminescence|triboluminescent]], [[chirality (chemistry)|chiral]] (hence optically active if not [[racemic mixture|racemic]])
| 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, [[crystalline]] [[mineral]] composed of silica ([[silicon dioxide]]). The [[Atom|atoms]] are linked in a continuous framework of SiO<sub>4</sub> silicon–oxygen [[Tetrahedral molecular geometry|tetrahedra]], with each oxygen being shared between two tetrahedra, giving an overall [[chemical formula]] of [[Silicon dioxide|SiO<sub>2</sub>]]. Quartz is, therefore, classified structurally as a [[Silicate mineral#Tectosilicates|framework silicate mineral]] and compositionally as an [[oxide mineral]]. Quartz is the second most abundant [[mineral]] in [[Earth]]'s [[continental crust]], behind [[feldspar]].<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 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 [[gemstone]]s. Since antiquity, varieties of quartz have been the most commonly used minerals in the making of [[Jewellery|jewelry]] and [[hardstone carving]]s, especially in Europe and Asia.

Quartz is the [[mineral]] defining the value of 7 on the [[Mohs scale of hardness]], a qualitative [[Scratch hardness|scratch]] method for determining the hardness of a material to abrasion.