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 573°C (846K; 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 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 Quarz,[10] which had the same form in the first half of the 14th century in Middle High German and in East Central German[11] and which came from the Polish dialect term kwardy, which corresponds to the Czech term tvrdý ('hard').[12] Some sources, however, attribute the word's origin to the Saxon word Querkluftertz, meaning 'cross-vein ore'.[13][14]
The Ancient Greeks referred to quartz as κρύσταλλος (krustallos) meaning 'crystal', derived from the Ancient Greekκρύος (kruos) meaning 'icy cold', because some philosophers (including Theophrastus) believed the mineral to be a form of supercooled ice.[14] Today, the term rock crystal is sometimes used as an alternative name for transparent, coarsely crystalline quartz.[15][16]:205
Early studies
Roman naturalist Pliny 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 near glaciers in the Alps, but not 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 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.[19]
Crystal habit and structure
Crystal structure of α-quartz (red balls are oxygen, gray are silicon)
Crystal structure of β-quartz
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 573°C (1,063°F; 846K) 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.[20]
Both polymorphs of quartz can occur in two different space groups depending on the chirality. Above the transition temperature, α-quartz in P3121 (space group 152) becomes β-quartz in P6422 (space group 181), and α-quartz in P3221 (space group 154) becomes β-quartz in P6222 (space group 180).[21]
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,[22] and this can result in significant microfracturing in ceramics during firing,[23] in ornamental stone after a fire[24] and in rocks of the Earth's crust exposed to high temperatures,[25] 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.[9][16]: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.[26] 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.[27]
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.[28] These color differentiations arise from the presence of impurities which change the molecular orbitals, causing some electronic transitions that absorb electromagnetic energy from the visible spectrum. The unabsorbed wavelengths are transmitted and give rise to the mineral's visible color.[29]
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).[30] Today, the microcrystalline and cryptocrystalline varieties are commonly grouped together and referred to as chalcedony.[30][31] However, in the scientific literature, chalcedony is a specific form of silica consisting of fine intergrowths of both quartz and its monoclinicpolymorph, moganite.[32][31] Chalcedony is commonly translucent to opaque, while the macrocrystalline varieties of quartz tend to be more transparent.[33][30] Color is a secondary identifier for the cryptocrystalline varieties and a primary identifier for the macrocrystalline varieties.[33][34]
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.
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 aluminumcolor 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.
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.
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
Rose quartz
Euhedral rose quartz (pink quartz) cluster from Minas Gerais, Brazil
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%.[64] Quartz is a defining constituent of granite and other felsicigneous 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.[9] 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.[65]
While the majority of quartz crystallizes from molten magma, quartz also chemically precipitates from hot hydrothermalveins as gangue, sometimes with ore minerals such as gold, silver and copper. Large crystals of quartz are found in magmatic pegmatites.[9] Well-formed crystals may reach several meters in length and weigh hundreds of kilograms.[66]
The largest documented single crystal of quartz was found near Itapore, Goiaz, Brazil; it measured approximately 6.1m ×1.5m ×1.5m (20ft ×5ft ×5ft) and weighed over 39,900kg (88,000lb).[67]
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.[68][69]
Pressure-temperature diagram showing the stability ranges for the two forms of quartz and some other forms of silica[70]
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.[16]:201–202Moganite is a monoclinic polymorph. Lechatelierite is an amorphous silica glass SiO2 which is formed by lightning strikes in quartz sand.[71]
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.[72] 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.[73][74]
Synthetic and artificial treatments
A synthetic quartz crystal grown by the hydrothermal method, about 19 centimetres (7.5in) long and weighing about 127 grams (4.5oz)
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.[75] Prasiolite, an olive-colored material, is produced by heat treatment;[76] natural prasiolite has also been observed in Lower Silesia in Poland.[77] Although citrine occurs naturally, the majority is the result of heat-treating amethyst or smoky quartz.[76]Carnelian has been heat-treated to deepen its color since prehistoric times.[78] 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.[79][9][80][81] Like other crystals, quartz may be coated with metal vapors to give it an attractive sheen.[82][83]
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.[85] However, the quality and size of the crystals that were produced by these early efforts were poor.[86]
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 siliconboules to be sliced into silicon wafers in the semiconductor industry, are expensive and rare. These high-purity quartzes are defined as containing less than 50 ppm of impurity elements.[87] A major mining location for high-purity quartz is the Spruce Pine Mining District in Spruce Pine, North Carolina, United States.[88] Quartz may also be found in Caldoveiro Peak in Asturias, Spain.[89]
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.[90] 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.[91][92] (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 (3.8cm) in diameter, the largest at that time.[93][94] 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.[81]
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.[95][96]George Washington Pierce designed and patented quartz crystal oscillators in 1923.[97][98][99] 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.[100] 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.[101]
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.[102]
Synthetic quartz crystals produced in the autoclave shown in Western 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.[103] 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.[104]
123Deer, 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.
↑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.
↑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. Retrieved 21 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. hdl:10810/78341.
1234Nesse, 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). On page 272Archived 4 September 2015 at the Wayback 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; … "
↑"Quartz-beta". mindat.org. Hudson Institute of Mineralogy. Retrieved 8 December 2025.
↑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.
↑"Cotterite". Mindat.org. Retrieved 13 January 2026.
↑Roycroft, P.D. (2016). "Cotterite: Historical review; extant specimens; etymology of 'Cotterite' and the genealogy of 'Miss Cotter'; new observations on the Cotterite texture". Irish Journal of Earth Sciences. 34: 45–78. doi:10.3318/ijes.2016.34.45.
↑Rickwood, P. C. (1981). "The largest crystals"(PDF). American Mineralogist. 66: 885–907 (903). Archived(PDF) from the original on 25 August 2013. Retrieved 7 March 2013.
↑McMillen, Allen. "Quartz Mining". Encyclopedia of Arkansas. Central Arkansas Library System. Retrieved 28 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 8days 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.
You are visitor 01402503 — GeezerVison does not store the pages you look up. Best viewed with Netscape Navigator 4.7 or Internet Explorer 6 at 800×600. No cookies required.
_2_(36619574200).jpg)
.jpg)
_1.jpg)
.jpg)
.jpg)
.jpg)
_(32734668126).jpg)
.jpg)
.jpg)
_10.jpg)
.jpg)
