Quartz exists in two forms, the normal α-quartz and the high-temperature β-quartz, both of which arechiral. The transformation from α-quartz to β-quartz takes place abruptly at 573 °C (846 K; 1,063 °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 asgemstones. Since antiquity, varieties of quartz have been the most commonly used minerals in the making ofjewelry andhardstone carvings, especially in Europe and Asia.
Quartz is themineral defining the value of 7 on theMohs scale of hardness, a qualitativescratch method for determining the hardness of a material to abrasion.
The wordquartz is derived from theGerman wordQuarz,[10] which had the same form in the first half of the 14th century inMiddle High German and inEast Central German[11] and which came from thePolishdialect termkwardy, which corresponds to theCzech termtvrdý ("hard").[12] Some sources, however, attribute the word's origin to theSaxon wordQuerkluftertz, meaningcross-vein ore.[13][14]
TheAncient Greeks referred to quartz asκρύσταλλος (krustallos) meaning "crystal", derived from theAncient Greekκρύος (kruos) meaning "icy cold", because somephilosophers (includingTheophrastus) believed the mineral to be a form of supercooledice.[14] Today, the termrock crystal is sometimes used as an alternative name for transparent, coarsely crystalline quartz.[15][16]: 205
Roman naturalistPliny the Elder believed quartz to be ice, permanently frozen after great lengths of time.[17] He supported this idea by saying that quartz is found nearglaciers in theAlps, but in warm climates. This idea persisted until at least the 17th century.[18]
In the 17th century,Nicolas Steno's study of quartz paved the way for moderncrystallography. 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 thelaw of constancy of interfacial angles.[19]
Crystal structure of α-quartz (red balls are oxygen, gray are silicon)
Crystal structure of β-quartz
A chiral pair of α-quartz
Quartz belongs to thetrigonal crystal system at room temperature and to thehexagonal crystal system above 573 °C (846 K; 1,063 °F). The former is called α-quartz; the latter is β-quartz. Theideal crystal shape is a six-sidedprism terminating with six-sided pyramid-likerhombohedrons at each end. In nature, quartz crystals are oftentwinned (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 appearmassive.[9][16]: 202–204
Well-formed crystals typically form as adruse (a layer of crystals lining a void), of which quartzgeodes are particularly fine examples.[20] 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, withingypsum.[21]
α-quartz crystallizes in the trigonal crystal system,space groupP3121 orP3221 (space group 152 or 154 resp.) depending on the chirality. Above 573 °C (846 K; 1,063 °F), α-quartz inP3121 becomes the more symmetric hexagonalP6422 (space group 181), and α-quartz inP3221 goes to space groupP6222 (no. 180).[22]
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.[9][16]: 201 However, there is a significant change in volume during this transition,[23] and this can result in significant microfracturing in ceramics during firing,[24] in ornamental stone after a fire[25] and in rocks of the Earth's crust exposed to high temperatures,[26] thereby damaging materials containing quartz and degrading their physical and mechanical properties.
This article or sectionis undergoing significant expansion or restructuring. You are welcome to assist in its construction by editing it as well. If this article or sectionhas not been edited in several days, please remove this template. If you are actively editing this article or section, you can replace this template with{{in use|5 minutes}}.This article waslast edited byDritto1010(talk |contribs) 31 minutes ago.(Updatetimer)
Pure quartz, traditionally called rock crystal or clear quartz, is colorless andtransparent or translucent. Colored varieties of quartz are common and includecitrine,rose quartz,amethyst,smoky quartz, milky quartz, and others.[27] 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]
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 areaggregates 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 anoptical microscope (sub-microscopic).[28] Today, the microcrystalline and cryptocrystalline varieties are commonly grouped together and referred to aschalcedony.[28][29] However, in the scientific literature, chalcedony is a specific form ofsilica consisting of fine intergrowths of both quartz and itsmonoclinicpolymorph,moganite.[30][29] Chalcedony is commonly translucent to opaque, while the macrocrystalline varieties of quartz tend to be more transparent.[31][28] Color is a secondary identifier for the cryptocrystalline varieties and a primary identifier for the macrocrystalline varieties.[31][better source needed]
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 ametrine is partially heat-treated or artificially irradiated amethyst.
Natural: yellow to yellow-green or yellow-orange, often with smoky hues
Heat-treated amethyst: yellow-orange, orange, red, brown
Natural: no scientific consensus (eitheraluminumcolor centers or trace iron impurities)
Heat-treated amethyst: trace amounts of iron oxides (hematite andgoethite)
Natural citrine is rare; most "citrine" sold commercially is heat-treated amethyst or sometimes heat-treated smoky quartz. Quartz colored yellow from stains, coatings, or inclusions is generally not considered citrine.
While the majority of quartz crystallizes from moltenmagma, quartz also chemically precipitates from hothydrothermalveins asgangue, sometimes withore minerals such as gold, silver and copper. Large crystals of quartz are found in magmaticpegmatites.[9] Well-formed crystals may reach several meters in length andweigh hundreds of kilograms.[58]
The largest documented single crystal of quartz was found nearItapore,Goiaz, Brazil; it measured approximately 6.1 m × 1.5 m × 1.5 m (20 ft × 5 ft × 5 ft) and weighed over 39,900 kg (88,000 lb).[59]
Quartz is extracted fromopen-pit mines. Miners occasionally use explosives to expose deep pockets of quartz. More frequently,bulldozers andbackhoes 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.[60][61]
Pressure-temperature diagram showing the stability ranges for the two forms of quartz and some other forms of silica[62]
Tridymite andcristobalite are high-temperaturepolymorphs of SiO2 that occur in high-silicavolcanic 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.[16]: 201–202 Moganite is a monoclinic polymorph.Lechatelierite is anamorphous silicaglass SiO2 which is formed bylightning strikes in quartzsand.[63]
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.[64] Crystalline silica of respirable size is a recognized humancarcinogen and may lead to other diseases of the lungs such assilicosis andpulmonary fibrosis.[65][66]
A synthetic quartz crystal grown by thehydrothermal method, about 19 centimetres (7.5 in) long and weighing about 127 grams (4.5 oz)
Not all varieties of quartz are naturally occurring. Some clear quartz crystals can be treated using heat orgamma 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.[67]
Prasiolite, an olive-colored material, is produced by heat treatment;[68] natural prasiolite has also been observed in Lower Silesia in Poland.[69] Although citrine occurs naturally, the majority is the result of heat-treating amethyst or smoky quartz.[68]Carnelian has been heat-treated to deepen its color since prehistoric times.[70]
Because natural quartz is oftentwinned, synthetic quartz is produced for use in industry. Large, flawless single crystals are synthesized in anautoclave via thehydrothermal process.[71][9][72]
Whilejade has been the most prized semi-precious stone for carving inEast Asia andpre-Columbian America since earliest times, in Europe and the Middle East different varieties of quartz were the most commonly used for the various types ofjewelry andhardstone carving, includingengraved gems andcameo 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 geologistKarl Emil von Schafhäutl (1803–1890) was the first person to synthesize quartz when in 1845 he created microscopic quartz crystals in apressure cooker.[76] However, the quality and size of the crystals that were produced by these early efforts were poor.[77]
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 largesiliconboules to be sliced into siliconwafers in thesemiconductor industry, are expensive and rare. These high-purity quartz are defined as containing less than 50 ppm of impurity elements.[78] A major mining location for high-purity quartz is theSpruce Pine Mining District inSpruce Pine, North Carolina, United States.[79] Quartz may also be found inCaldoveiro Peak inAsturias, Spain.[80]
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.[81] After the war, many laboratories attempted to grow large quartz crystals. In the United States, the U.S. Army Signal Corps contracted withBell Laboratories and with theBrush Development Company of Cleveland, Ohio to synthesize crystals following Nacken's lead.[82][83] (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.[84][85] 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.[72]
An early use of the piezoelectricity of quartz crystals was inphonograph pickups. One of the most common piezoelectric uses of quartz today is as acrystal oscillator. Also called a quartz oscillator or resonator, it was first developed byWalter Guyton Cady in 1921.[86][87]George Washington Pierce designed and patentedquartz crystal oscillators in 1923.[88][89][90] Thequartz 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.[91] 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 thequartz crystal microbalance and inthin-film thickness monitors.[92]
Rock crystal jug with cut festoon decoration by aMilan workshop from the second half of the 16th century,National Museum,Warsaw. Milan, apart fromPrague andFlorence, was the mainRenaissance centre for crystal cutting.[93]
Synthetic quartz crystals produced in the autoclave shown inWestern Electric's pilot hydrothermal quartz plant in 1959
Fatimid ewer in carved rock crystal (clear quartz) with gold lid,c. 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.[94] The popularity ofcrystal healing has increased the demand for natural quartz crystals, which are now often mined indeveloping countries using primitive mining methods, sometimes involvingchild labor.[95]
^abcDeer, W. A.; Howie, R.A.; Zussman, J. (1966).An introduction to the rock-forming minerals. New York: Wiley. pp. 340–355.ISBN0-582-44210-9.
^Antao, S. M.; Hassan, I.; Wang, J.; Lee, P. L.; Toby, B. H. (1 December 2008). "State-Of-The-Art High-Resolution Powder X-Ray Diffraction (HRPXRD) Illustrated with Rietveld Structure Refinement of Quartz, Sodalite, Tremolite, and Meionite".The Canadian Mineralogist.46 (6):1501–1509.doi:10.3749/canmin.46.5.1501.
^Anthony, John W.; Bideaux, Richard A.; Bladh, Kenneth W.; Nichols, Monte C., eds. (29 January 1990)."Quartz"(PDF).Handbook of Mineralogy. Vol. III (Halides, Hydroxides, Oxides). Chantilly, VA: Mineralogical Society of America.ISBN0962209724.Archived(PDF) from the original on 1 April 2010. Retrieved21 October 2009.
^Morgado, Antonio; Lozano, José Antonio; García Sanjuán, Leonardo; Triviño, Miriam Luciañez; Odriozola, Carlos P.; Irisarri, Daniel Lamarca; Flores, Álvaro Fernández (December 2016). "The allure of rock crystal in Copper Age southern Iberia: Technical skill and distinguished objects from Valencina de la Concepción (Seville, Spain)".Quaternary International.424:232–249.Bibcode:2016QuInt.424..232M.doi:10.1016/j.quaint.2015.08.004.
^abcdNesse, William D. (2000).Introduction to mineralogy. New York: Oxford University Press.ISBN9780195106916.
^Tutton, A.E. (1910). "Rock crystal: its structure and uses".RSA Journal.59: 1091.JSTOR41339844.
^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). Onpage 272Archived 4 September 2015 at theWayback Machine, 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; … "
^Sinkankas, John (1964).Mineralogy for amateurs. Princeton, N.J.: Van Nostrand. pp. 443–447.ISBN0442276249.{{cite book}}:ISBN / Date incompatibility (help)
^Knapek, Michal; Húlan, Tomáš; Minárik, Peter; Dobroň, Patrik; Štubňa, Igor; Stráská, Jitka; Chmelík, František (January 2016). "Study of microcracking in illite-based ceramics during firing".Journal of the European Ceramic Society.36 (1):221–226.doi:10.1016/j.jeurceramsoc.2015.09.004.
^Rickwood, P. C. (1981)."The largest crystals"(PDF).American Mineralogist.66: 885–907 (903).Archived(PDF) from the original on 25 August 2013. Retrieved7 March 2013.
^McMillen, Allen."Quartz Mining".Encyclopedia of Arkansas. Central Arkansas Library System. Retrieved28 November 2020.
^Groman-Yaroslavski, Iris; Bar-Yosef Mayer, Daniella E. (June 2015). "Lapidary technology revealed by functional analysis of carnelian beads from the early Neolithic site of Nahal Hemar Cave, southern Levant".Journal of Archaeological Science.58:77–88.Bibcode:2015JArSc..58...77G.doi:10.1016/j.jas.2015.03.030.
^Walker, A. C. (August 1953). "Hydrothermal Synthesis of Quartz Crystals".Journal of the American Ceramic Society.36 (8):250–256.doi:10.1111/j.1151-2916.1953.tb12877.x.
^von Schafhäutl, Karl Emil (10 April 1845)."Die neuesten geologischen Hypothesen und ihr Verhältniß zur Naturwissenschaft überhaupt (Fortsetzung)" [The latest geological hypotheses and their relation to science in general (continuation)].Gelehrte Anzeigen.20 (72).München: im Verlage der königlichen Akademie der Wissenschaften, in Commission der Franz'schen Buchhandlung:577–584.OCLC1478717. 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.)
^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.
^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",U.S. patent 2,674,520; filed: 11 April 1950; issued: 6 April 1954.
Sobek, Andrew R. and Hale, Danforth R. "Method and apparatus for growing single crystals of quartz",U.S. patent 2,675,303; filed: 11 April 1950; issued: 13 April 1954.
Sawyer, Charles B. "Production of artificial crystals",U.S. patent 3,013,867; filed: 27 March 1959; issued: 19 December 1961. (This patent was assigned to Sawyer Research Products of Eastlake, Ohio.)
^Pierce, G. W. (1923). "Piezoelectric crystal resonators and crystal oscillators applied to the precision calibration of wavemeters".Proceedings of the American Academy of Arts and Sciences.59 (4):81–106.doi:10.2307/20026061.hdl:2027/inu.30000089308260.JSTOR20026061.
^Pierce, George W. "Electrical system",U.S. patent 2,133,642, filed: 25 February 1924; issued: 18 October 1938.
^The International Antiques Yearbook. Studio Vista Limited. 1972. p. 78.Apart from Prague and Florence, the main Renaissance centre for crystal cutting was Milan.
_1.jpg)
.jpg)
.jpg)
.jpg)
_(32734668126).jpg)
.jpg)
.jpg)
_10.jpg)
.jpg)
_2_(36619574200).jpg)
.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.[93]](/mt/?noimg=&dark=on&url=https%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aMilan_Jug_with_cut_festoon_decoration.jpg)
