View source for Quartz

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{{Infobox mineral
| name        = '''Quartz'''
| category    = Mineral
| boxwidth    = 
| boxbgcolor  = 
| image       = USDA Mineral Quartz Crystal 93c3951.jpg
| imagesize   = 200
| caption     = Quartz crystal group from [[Arkansas]]
| formula     = [[Silica]] (silicon dioxide, SiO<sub>2</sub>)
| molweight   = 
| color       = Clear (if no impurities); also see Varieties
| habit       = 6-sided prism ending in 6-sided pyramid (typical)
| system      = [[rhombohedral]] class 32
| twinning    = Dauphine law, Brazil law and Japan law
| cleavage    = None
| fracture    = Conchoidal
| mohs        = 7 - lower in impure varieties
| luster      = Vitreous/glossy 
| 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 constant; variable in impure varieties
| density     = 
| melt        = 1650 (±75) °C
| fusibility  = 
| diagnostic  = 
| solubility  = 11.0 +/- 1.1 PPM @ 25 C
| diaphaneity = Transparent to translucent
| other       = Piezoelectric
}}

'''Quartz''' (from [[German language|German]] {{Audio|De-Quarz.ogg|'''Quarz'''}}<ref>[http://german.about.com/library/blvoc_gerloan.htm German Loan Words in English<!-- Bot generated title -->]</ref>) is the  most abundant [[mineral]] in the [[Earth]]'s [[continental crust]] (although [[feldspar]] is more common in the world as a whole). It is made up of a [[Crystal structure|lattice]] of [[silica]] ({{silicon}}{{oxygen|2}}) [[tetrahedra]]. Quartz has a hardness of 7 on the [[Mohs scale]] and a [[density]] of 2.65 g/cm³. 

==Crystal habit==
Quartz belongs to the [[rhombohedral crystal system]]. The [[crystal habit|ideal crystal shape]] is a six-sided [[prism (geometry)|prism]] terminating with six-sided [[pyramid]]s at each end. In nature quartz crystals are often [[Crystal twinning|twinned]], 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. Well-formed crystals typically form in a 'bed' that has unconstrained growth into a void, but because the crystals must be attached at the other end to a matrix, only one termination pyramid is present. A quartz [[geode]] is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward.

It looks very nice

==Varieties==

Pure quartz is colorless or white, colored varieties include rose quartz, [[amethyst]], smoky quartz, milky quartz, and others. Quartz goes by an array of different names. The most important distinction between types of quartz is that of ''macrocrystalline'' (individual crystals visible to the unaided eye) and the [[microcrystalline]] or [[cryptocrystalline]] varieties (aggregates of crystals visible only under high magnification). [[Chalcedony]] is a generic term for cryptocrystalline quartz. The cryptocrystalline varieties are either translucent or mostly opaque, while the transparent varieties tend to be macrocrystalline.

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. This does not always hold true.

{| class="wikitable"
|+ Major Varieties
|  [[Chalcedony]]  || Any cryptocrystalline quartz, although generally only used for white or lightly colored material. Otherwise more specific names are used.
|-----
| [[Agate]]        || Multi-colored, banded chalcedony, semi-translucent to translucent
|-----
| [[Onyx]]         || Agate where the bands are straight, parallel and consistent in size.
|-----
| [[Jasper]]       || Opaque chalcedony, typically red to brown
|-----
| [[Aventurine]]   || Translucent chalcedony with small inclusions (usually mica) that shimmer.
|-----
| [[Tiger's eye]]  || Fibrous gold to red-brown coloured quartz, exhibiting [[chatoyancy]].
|-----
| Rock crystal     || Clear, colorless
|-----
| [[Amethyst]]     || Purple, transparent
|-----
| [[Citrine]]      || Yellow to reddish orange to brown, greenish yellow
|-----
| [[Prasiolite]]   || Mint green, transparent
|-----
| [[Rose quartz]]  || Pink, translucent, may display [[asterism (gemmology)|diasterism]] 
|-----
| Rutilated quartz || Contains acicular (needles) inclusions of [[rutile]]
|----
| [[Milk quartz]]  || White, translucent to opaque, may display diasterism
|-----
|[[Smoky quartz]]  || Brown to grey, opaque
|----
|[[Morion]]        || Dark-brown, opaque
|----
| [[Carnelian]]    || Reddish orange chalcedony, translucent
|}

<gallery>
Image:IMG 5779.jpg|<center>Rose quartz</center>
Image:QuartzUSGOV.jpg|<center>Milk quartz</center>
Image:Kwarc z rutylem.JPG|<center>Rutilated quartz crystal</center>
</gallery>
===Synthetic and artificial treatments===
[[Image:Synthetic quartz crystal.jpg|thumb|A synthetic quartz crystal grown by the [[Hydrothermal synthesis|hydrothermal method]], about 19 cm long and weights about 127 grams]]
Not all varieties of quartz are naturally occurring.  [[Prasiolite]], an olive colored material, is produced by heat treatment; natural prasiolite has also been observed in Lower Silesia in Poland. Although [[citrine]] occurs naturally, the majority is the result of heat-treated amethyst. [[Carnelian]] is widely heat-treated to deepen its color.

Due to natural quartz being so often [[crystal twinning|twinned]], much of the quartz used in industry is synthesized. Large, flawless and untwinned crystals are produced in an [[autoclave]] via the [[Hydrothermal synthesis|hydrothermal process]]; [[emerald]]s are also synthesized in this fashion. While these are still commonly referred to as quartz, the correct term for this material is [[silicon dioxide]].

==Occurrence==
Quartz occurs in [[hydrothermal]] [[Vein (geology)|veins]] and [[pegmatite]]s. Well-formed crystals may reach several meters in length and [[mass|weigh]] hundreds of kilograms. These veins may bear [[precious metals]] such as [[gold]] or [[silver]], and form the quartz ores sought in [[mining]]. Erosion of pegmatites may reveal expansive pockets of crystals, known as "cathedrals."

Quartz is a common constituent of [[granite]], [[sandstone]], [[limestone]], and many other [[igneous]], [[sedimentary]], and [[metamorphic rock|metamorphic]] rocks.

==Related silica minerals==
[[Tridymite]] and [[cristobalite]] are high-temperature [[Polymorphism (materials science)|polymorph]]s of SiO<sub>2</sub> that occur in high-silica [[volcanic]] rocks. [[Coesite]] is a denser polymorph of quartz 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 quartz found in some meteorite impact sites. [[Lechatelierite]] is an [[amorphous]] silica [[glass]] SiO<sub>2</sub> which is formed by [[lightning]] strikes in quartz [[sand]].

==History==
[[Image:Transparency.jpg|right|thumb|200px|Quartz crystal showing [[Transparency (optics)|transparency]].]]
The name "quartz" comes from the German "Quarz", which is of Slavic origin (Czech miners called it ''křemen''). Other sources insist the name is from the [[Upper Saxon|Saxon]] word "Querkluftertz", meaning ''cross-vein ore''.<ref>[http://www.mineralatlas.com/mineral%20general%20descriptions/Q/quartzpcd.htm ''Mineral Atlas'', Queensland University of Technology]</ref>

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, eg. [[Newgrange]] or [[Carrowmore]] in the [[Republic of Ireland]]. The [[Irish language|Irish]] word for quartz is ''grian cloch'', which means 'stone of the sun'.

Roman naturalist [[Pliny the Elder]] believed quartz to be water [[ice]], permanently frozen after great lengths of time.  (The word "crystal" comes from the Greek word for ice.) 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. He also knew of the ability of quartz to split light into a [[spectrum]].  This idea persisted until at least the 1600s.

[[Nicolas Steno]]'s study of quartz paved the way for modern [[crystallography]]. He discovered that no matter how distorted a quartz crystal, the long prism faces always made a perfect 60 degree angle.

[[Charles Sawyer]] invented the commercial quartz crystal manufacturing process in [[Cleveland]], [[Ohio]], [[United States]].  This initiated the transition from mined and cut quartz for electrical appliances to manufactured quartz. 

Quartz's [[piezoelectric]] properties were discovered by [[Jacques Curie|Jacques]] and [[Pierre Curie]] in 1880.  The [[quartz oscillator]] or resonator was first developed by [[Walter Guyton Cady]] in 1921 [http://www.hrw.com/science/si-science/chemistry/careers/quartz/inventors/cady.html]. George Washington Pierce designed and patented quartz crystal oscillators in 1923 [http://www.hrw.com/science/si-science/chemistry/careers/quartz/inventors/pierce.html]. Warren Marrison created the first quartz oscillator clock based on the work of Cady and Pierce in 1927 [http://www.hrw.com/science/si-science/chemistry/careers/quartz/inventors/clock.html].

Quartz crystals are rotary polar (see [[rotary polarization]]) and have the ability to rotate the plane of polarization of light passing through them.  They are also highly piezoelectric, becoming polarized with a negative charge on one end and a positive charge on the other when subjected to pressure.  They will vibrate if an alternating electric current is applied to them. This proves them to be highly important in commerce for making pressure gauges, oscillators, resonators and watches.

==Piezoelectricity==
Quartz crystals have [[piezoelectric]] properties, that is they develop an electric potential upon the application of mechanical stress. An early use of this property of quartz crystals was in [[phonograph]] pickups. One of the most common piezoelectric uses of quartz today is as a [[crystal oscillator]].  The [[quartz clock]] is a familiar device using the mineral. 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 monitor]]s.

==See also==
{{wikisourcepar|EB1911:Quartz}}
*[[Aqua aura]]
*[[Azeztulite]]
*[[Flame aura]]
*[[Fused quartz]]
*[[List of minerals]]
*[[Shocked quartz]]
*[[Quartz reef mining]]

==References==
{{Commons|Quartz}}
*Hurlbut, Cornelius S.; Klein, Cornelis, 1985, ''Manual of Mineralogy,'' 20th ed., ISBN 0-471-80580-7
* [http://www.quartzpage.de/ Quartz varieties, properties, crystal morphology.  Photos and illustrations]
* [http://rockhoundingar.com/quartz.html ''Arkansas quartz'', Rockhounding Arkansas]
* [http://www.minsocam.org/MSA/collectors_corner/arc/silicanom.htm Gilbert Hart ''Nomenclature of Silica'', American Mineralogist, Volume 12, pages 383-395, 1927]
* [http://www.mindat.org/min-3337.html Mindat.org]
* [http://labs.sci.qut.edu.au/minerals/mineral%20general%20descriptions/Q/quartzpcd.htm Queensland University of Technology] Origin of the word quartz.
* [https://goby.nrl.nav.mil/branch/UFFC_Archive/cd01/fc/proceed/1959/proceed/s5910462.pdf PDF of Charles Sawyer's cultured quartz process description]
* [http://www.hrw.com/science/si-science/chemistry/careers/quartz/inventors/before.html Smithsonian Institute, Inventors of quartz oscillating devices]
*http://www.webmineral.com/data/Quartz.shtml
*http://www.gemstone.org/gem-by-gem/english/quartz.html
*http://mineral.galleries.com/minerals/silicate/quartz/quartz.htm
*http://mineral.galleries.com/minerals/gemstone/rock_cry/rock_cry.htm
* [http://www.connogue.com/quartslab/html/terminology.html Terminology used to describe the characteristics of Quartz Crystals when used as oscillators]
*http://www.realgems.org/list_of_gemstones/quartz.html RealGems.org Quartz

{{reflist|2}}

{{Jewellery Materials}}

{{Silica minerals}}

[[Category:Quartz varieties]]
[[Category:Piezoelectric materials]]
[[Category:Dielectrics]]
[[Category:German loanwords]]

[[ar:مرو]]
[[bs:Kvarc]]
[[bg:Кварц]]
[[ca:Quars]]
[[cs:Křemen]]
[[da:Kvarts]]
[[de:Quarz]]
[[et:Kvarts]]
[[el:Χαλαζίας]]
[[es:Cuarzo]]
[[eo:Kvarco]]
[[fa:کوارتز]]
[[fr:Quartz (minéral)]]
[[gl:Cuarzo]]
[[ko:석영]]
[[hr:Kvarc]]
[[id:Kuarsa]]
[[it:Quarzo]]
[[he:קוורץ]]
[[lv:Kvarcs]]
[[lb:Quarz]]
[[lt:Kvarcas]]
[[hu:Kvarc]]
[[mk:Кварц]]
[[ms:Kuarza]]
[[nl:Kwarts]]
[[ja:石英]]
[[no:Kvarts]]
[[nn:Kvarts]]
[[pl:Kwarc]]
[[pt:Quartzo]]
[[ro:Cuarţ]]
[[ru:Кварц]]
[[simple:Quartz]]
[[sk:Kremeň]]
[[sl:Kamena strela]]
[[sr:Кварц]]
[[fi:Kvartsi]]
[[sv:Kvarts]]
[[th:ควอตซ์]]
[[vi:Thạch anh]]
[[tr:Kuvars]]
[[uk:Кварц]]
[[zh:石英]]