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quartz

The most abundant and common mineral, consisting of crystalline silica (silicon dioxide, SiO2), crystallizing in the trigonal system. It has a hardness of 7 on the Mohs' scale. Well-formed ...

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A Dictionary of Chemistry (8 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Science and technology, Chemistry
Length:
146 words

... The most abundant and common mineral, consisting of crystalline silica (silicon dioxide, SiO 2 ), crystallizing in the trigonal system. It has a hardness of 7 on the Mohs scale. Well-formed crystals of quartz are six-sided prisms terminating in six-sided pyramids. Quartz is ordinarily colourless and transparent, in which form it is known as rock crystal . Coloured varieties, a number of which are used as gemstones, include amethyst , citrine quartz (yellow), rose quartz (pink), milk quartz (white), smoky quartz (grey-brown), chalcedony , agate , and ...

quartz

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The Concise Oxford Dictionary of Archaeology (2 ed.)

Reference type:
Subject Reference
Current Version:
2009
Subject:
Archaeology, History
Length:
91 words

... [Ma] Opaque white crystalline silicate stone found in many parts of the world and variously used for toolmaking and in ceremonial contexts. In Atlantic Europe white quartz pebbles were used as talismans, perhaps representing the soul of a person, from the early Neolithic through into early Christian times. White quartz is frequently found deposited around stone circles and passage graves . Quartzite is a metamorphic rock consisting mainly of quartz which was also used for making tools and weapons, as it is hard and has conchoidal fracturing properties...

quartz

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The Concise Oxford Dictionary of Art Terms (2 ed.)

Reference type:
Subject Reference
Current Version:
2010
Subject:
Art & Architecture
Length:
60 words

... A mineral form of silica, used since ancient times in sculpture and particularly valued when tinted rose or smoky grey, or when transparent (when it is known as rock crystal ). Many hardstones are types of quartz, including agate , amethyst , bloodstone, chalcedony , and cornelian , and were most frequently fashioned into miniature works of...

quartz

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World Encyclopedia

Reference type:
Subject Reference
Current Version:
2004
Subject:
Encyclopedias
Length:
100 words

... Rock-forming mineral, the natural form of silicon dioxide (silica), SiO 2 . It is widely distributed, occurring in igneous and metamorphic rocks, and in clastic sediments. It is also found in mineral veins. It forms six-sided crystals. Pure quartz is clear and colourless but the mineral may be coloured by impurities. The most common varieties are colourless quartz (rock crystal), rose, yellow, milky and smoky. The most usual cryptocrystalline varieties, whose crystals can be seen only under a microscope, are chalcedony and flint . Quartz crystals...

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A Dictionary of Electronics and Electrical Engineering (5 ed.)

Reference type:
Subject Reference
Current Version:
2018

... Naturally occurring crystalline silicon dioxide (SiO 2 ). It exhibits marked piezoelectric properties and is frequently used as the piezoelectric crystal in piezoelectric oscillators . It also exhibits marked dielectric strength . Quartz may be readily drawn into extremely fine uniform filaments that are very strong, elastic, and physically and chemically stable. Such quartz fibres are frequently used as torsion threads in delicate measuring instruments, such as electrometers . ...

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A Dictionary of Geology and Earth Sciences (5 ed.)

Reference type:
Subject Reference
Current Version:
2020

... ( rock crystal ) Widely distributed rock‐forming silicate mineral SiO 2 with the related semi‐precious varieties rose quartz (pink), amethyst (purple), cairngorm (dark brown and similar to smoky quartz, although the original cairngorms from the Scottish mountain range were of topaz ), citrine (light brown); sp. gr. 2.65; hardness 7; trigonal ; commonly colourless or white, but can occur in a variety of colours; vitreous lustre ; crystals usually six‐sided prisms terminated by six‐faced pyramids, the prisms often striated, also occurs...

quartz

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Oxford Dictionary of Biochemistry and Molecular Biology (2 ed.)

Reference type:
Subject Reference
Current Version:
2008
Subject:
Science and technology, Life Sciences
Length:
40 words

... a colourless, often transparent, glassy form of silica, SiO 2 , used in optical devices and cuvettes because of its transparency to near‐ultraviolet radiation. It is enantiomorphous, the right‐ and left‐handed forms rotating the plane of polarized light in opposite...

quartz

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A Dictionary of Construction, Surveying and Civil Engineering (2 ed.)

Reference type:
Subject Reference
Current Version:
2020

... A crystalline mineral, typically transparent, with a hardness of 7 (on the Mohs scale of hardness) and density of 2.65 Mg/m 3 . Common to granite , and the main element found in sand, gravel, and sandstone...

quartz

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A Dictionary of Physics (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Physics
Length:
70 words

...quartz The most abundant and common mineral, consisting of crystalline silica (silicon dioxide, SiO 2 ), crystallizing in the trigonal system. It has a hardness of 7 on the Mohs’ scale. The mineral has the property of being piezoelectric and hence is used to make oscillators for clocks ( see quartz clock ), radios, and radar instruments. It is also used in optical instruments and in glass, glaze, and...

quartz

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Alex Maltman

The Oxford Companion to Wine (4 ed.)

Reference type:
Subject Reference
Current Version:
2015

... , silicon dioxide (silica), a very common rock-forming mineral. It is seen as glassy, colourless grains in rocks such as granite and sandstone , producing sandy soils of low fertility. It also occurs as opaque white veins filling gashes in bedrock, which weathering loosens into fragments that become the milky white pebbles seen in many vineyard soils. See also geology . Alex...

quartz

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A Dictionary of Environment and Conservation (3 ed.)

Reference type:
Subject Reference
Current Version:
2017

... The most common rock‐forming mineral , composed of crystals of silicon dioxide (SiO 2 ), which may be glassy or...

secondary quartz

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A Dictionary of Geology and Earth Sciences (5 ed.)

Reference type:
Subject Reference
Current Version:
2020

...quartz Quartz formed as a cement during diagenesis...

quartz overgrowth

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A Dictionary of Geology and Earth Sciences (5 ed.)

Reference type:
Subject Reference
Current Version:
2020

... overgrowth The development of quartz cement around detrital grains , the quartz cement growing in optical continuity with the grains which they have...

quartz porphyry

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A Dictionary of Geology and Earth Sciences (5 ed.)

Reference type:
Subject Reference
Current Version:
2020

... porphyry ( elvan ) A porphyritic microgranite , microgranodiorite , or...

quartz wacke

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A Dictionary of Geology and Earth Sciences (5 ed.)

Reference type:
Subject Reference
Current Version:
2020

... wacke A sandstone containing more than 15% mud matrix , with over 95% of the grains being quartz . See dott classification...

quartz fibre

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A Dictionary of Mechanical Engineering (2 ed.)

Reference type:
Subject Reference
Current Version:
2019

...quartz fibre A fine quartz filament made from high-purity (typically 99.95%) silicon dioxide, which has a very low coefficient of thermal expansion , can be heated to about 1 000°C, and has excellent resistance to thermal shock . The fibres can be spun and...

quartz wedge

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A Dictionary of Forensic Science

Reference type:
Subject Reference
Current Version:
2013
Subject:
Science and technology, Law
Length:
29 words

... wedge In microscopy, a tool that can be used to determine the birefringence of a fibre, in conjunction with a polarizing microscope and a Michel–Levy chart...

quartz clock

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A Dictionary of Physics (8 ed.)

Reference type:
Subject Reference
Current Version:
2019
Subject:
Science and technology, Physics
Length:
150 words

...quartz clock A clock based on a piezoelectric crystal of quartz ( see piezoelectric effect ). Each quartz crystal has a natural frequency of vibration, which depends on its size and shape. If such a crystal is introduced into an oscillating electronic circuit that resonates at a frequency very close to that of the natural frequency of the crystal, the whole circuit (including the crystal) will oscillate at the crystal’s natural frequency and the frequency will remain constant over considerable periods (a good crystal will maintain oscillation for a year...

quartz-resonator transducer

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A Dictionary of Mechanical Engineering (2 ed.)

Reference type:
Subject Reference
Current Version:
2019

...quartz-resonator transducer A device that utilizes the piezoelectric properties of crystalline silicon dioxide (quartz crystal) in the measurement of force , pressure , or temperature , all of which when applied to a quartz crystal cause its mechanical resonant frequency to change. Quartz thermometers are based upon the near-linear temperature dependence of the resonant frequency. Quartz pressure transducers ( piezoquartz pressure transducers ) are particularly suited to measuring rapidly-varying pressure and pressure transients, typically at high...

quartz-tungsten-halogen light

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A Dictionary of Dentistry (2 ed.)

Reference type:
Subject Reference
Current Version:
2020
Subject:
Medicine and health, Dentistry
Length:
16 words

...-tungsten-halogen light n. The light source in many resin composite curing lights . See also curing light...

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