quartz

Information about quartz

Quartz

General
CategoryMineral
Chemical formulaSilica (silicon dioxide, SiO2)
Identification
ColorClear (if no impurities); also see Varieties
Crystal habit6-sided prism ending in 6-sided pyramid (typical)
Crystal systemrhombohedral class 32
TwinningDauphine law, Brazil law and Japan law
CleavageNone
FractureConchoidal
Mohs Scale hardness7 - lower in impure varieties
LusterVitreous/glossy
Refractive indexnω = 1.543 - 1.545 nε = 1.552 - 1.554
Optical PropertiesUniaxial (+)
Birefringence+0.009 (B-G interval)
PleochroismNone
StreakWhite
Specific gravity2.65 constant; variable in impure varieties
Melting point1650 (±75) °C
SolubilityH2O insoluble
DiaphaneityTransparent to translucent
Other CharacteristicsPiezoelectric


Quartz (from German Quarz (helpinfo)[1]) is the second most common mineral in the Earth's continental crust, feldspar being the first. It is made up of a lattice of silica (SiO2) 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 ideal crystal shape is a six-sided prism terminating with six-sided pyramids at each end. In nature quartz crystals are often 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.

Varieties

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.
Enlarge picture
Milky quartz
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Quartz with Rutile (~ 4 cm in size)
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.

Because natural quartz is so often twinned, much quartz used in industry is synthesized. Large, flawless and untwinned crystals are produced in an autoclave via the hydrothermal process: emeralds are also synthesized in this fashion.

Quartz occurs in hydrothermal veins and pegmatites. Well-formed crystals may reach several meters in length and 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 rocks.

Major Varieties
ChalcedonyAny cryptocrystalline quartz, although generally only used for white or lightly coloured material. Otherwise more specific names are used.
AgateMulti-coloured, banded Chalcedony, semi-translucent to translucent
OnyxAgate where the bands are straight, parallel and consistent in size.
JasperOpaque chalcedony, impure
AventurineTranslucent chalcedony with small inclusions (usually mica) that shimmer.
Tiger's eyeFibrous gold to red-brown coloured quartz, exhibiting chatoyancy.
Rock crystal or mountain crystalClear, colourless
AmethystPurple, transparent
CitrineYellow to reddish orange to brown, greenish yellow
PrasioliteMint green, transparent
Rose quartzPink, translucent, may display diasterism
Milk quartz or snow quartzWhite, translucent to opaque, may display diasterism
Smoky quartzBrown to grey, opaque
MorionDark-brown, opaque
CarnelianReddish orange chalcedony, translucent

Other silica mineral varieties

Tridymite and cristobalite are high-temperature polymorphs of SiO2 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 impace sites. Lechatelierite is an amorphous silica glass SiO2 which is formed by lightning strikes in quartz sand.

History

Enlarge picture
Quartz crystal showing 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 Saxon word "Querkluftertz", meaning cross-vein ore.[2]

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 Ireland. The 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, OH. This initiated the transition from mined and cut quartz for electrical appliances to manufactured quartz.

The quartz oscillator or resonator was first developed by Walter Guyton Cady in 1921 [1]. George Washington Pierce designed and patented quartz crystal oscillators in 1923 [2]. Warren Marrison created the first quartz oscillator clock based on the work of Cady and Pierce in 1927 [3].

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 generate an electric current 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 perhaps the most familiar device using the mineral. The same principle is also used for very accurate measurements of very small mass changes by means of the quartz crystal microbalance.

See also

References



 •  • [ e]
Gemstones and crystals
Gems:Aquamarine Emerald Jasper Lapis lazuli Pearl Peridot Ruby Sunstone Tiger's eye
Crystals:Agate Amethyst Chalcedony Diamond Pyrite Quartz Rhodochrosite Sapphire Topaz Tourmaline
A chemical formula is a concise way of expressing information about the atoms that constitute a particular chemical compound. A chemical formula is also a short way of showing how a chemical reaction occurs.
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silicon dioxide, also known as silica or silox (from the Latin "silex"), is the oxide of silicon, chemical formula SiO2, and has been known for its hardness since the 16th century.
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habit of crystals.

The many terms used by mineralogists to describe crystal habits are useful in communicating what specimens of a particular mineral often look like. Recognizing numerous habits helps a mineralogist to identify a large number of minerals.
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A crystal system is a category of space groups, which characterize symmetry of structures in three dimensions with translational symmetry in three directions, having a discrete class of point groups.
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rhombohedral (or trigonal) crystal system is one of the seven lattice point groups, named after the two-dimensional rhombus. A crystal system is described by three basis vectors.
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Crystal twinning occurs when two separate crystals share some of the same crystal lattice points in a symmetrical manner. The result is an intergrowth of two separate crystals in a variety of specific configurations. A twin boundary or composition surface separates the two crystals.
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Cleavage, in mineralogy, is the tendency of crystalline materials to split along definite planes, creating smooth surfaces, of which there are several named types:
  • Basal cleavage: cleavage parallel to the base of a crystal, or to the plane of the lateral axes.

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fracture is the (local) separation of a body into two, or more, pieces under the action of stress.

The word fracture is often applied to bones of living creatures, or to crystals or crystalline materials, such as gemstones or metal.
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The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in
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For other senses of this word, see lustre.


Lustre (American English: luster) is a description of the way light interacts with the surface of a crystal, rock, or mineral.
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The refractive index (or index of refraction) of a medium is a measure for how much the speed of light (or other waves such as sound waves) is reduced inside the medium. For example, typical glass has a refractive index of 1.
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Birefringence, or double refraction, is the decomposition of a ray of light into two rays (the ordinary ray and the extraordinary ray) when it passes through certain types of material, such as calcite crystals or boron nitride, depending on the polarization of
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The streak (also called powder color) of a mineral is the color of the powder produced when it is dragged across an unweathered surface. Unlike the apparent color of a mineral, which for most minerals can vary considerably, the trail of finely ground powder generally has a
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Please assist in recruiting an expert or [ improve this article] yourself. See the talk page for details. This article has been tagged since November 2006.
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The melting point of a crystalline solid is the temperature range at which it changes state from solid to liquid. Although the phrase would suggest a specific temperature and is commonly and incorrectly used as such in most textbooks and literature, most crystalline compounds
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Solubility is a physical property referring to the ability for a given substance, the solute, to dissolve in a solvent.[1] It is measured in terms of the maximum amount of solute dissolved in a solvent at equilibrium. The resulting solution is called a saturated solution.
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German language (Deutsch, ] (help info ) ) is a West Germanic language and one of the world's major languages.
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A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure and specific physical properties.
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EARTH was a short-lived Japanese vocal trio which released 6 singles and 1 album between 2000 and 2001. Their greatest hit, their debut single "time after time", peaked at #13 in the Oricon singles chart.
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The continental crust is the layer of granitic, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as continental shelves.
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Feldspar is the name of a group of rock-forming minerals which make up as much as 60% of the Earth's crust.[1]

Feldspars crystallize from magma in both intrusive and extrusive rocks, and they can also occur as compact minerals, as veins, and are also present in
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crystal structure is a unique arrangement of atoms in a crystal. A crystal structure is composed of a motif, a set of atoms arranged in a particular way, and a lattice. Motifs are located upon the points of a lattice, which is an array of points repeating periodically in three
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silicon dioxide, also known as silica or silox (from the Latin "silex"), is the oxide of silicon, chemical formula SiO2, and has been known for its hardness since the 16th century.
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Silicon (IPA: /ˈsɪlɪkən/ or /ˈsɪlɪˌkɑn/, Latin: silicium
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2, −1
(neutral oxide)
Electronegativity 3.44 (Pauling scale)
Ionization energies
(more) 1st: 1313.9 kJmol−1
2nd: 3388.3 kJmol−1
3rd: 5300.5 kJmol−1

Atomic radius 60 pm
Atomic radius (calc.
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For the academic journal, see Tetrahedron (journal).


A tetrahedron (plural: tetrahedra) is a polyhedron composed of four triangular faces, three of which meet at each vertex.
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The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material. It was created in 1812 by the German mineralogist Friedrich Mohs and is one of several definitions of hardness in
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In physics, density is mass m per unit volume V—how heavy something is compared to its size. A small, heavy object, such as a rock or a lump of lead, is denser than a lighter object of the same size or a larger object of the same weight, such as pieces of
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rhombohedral (or trigonal) crystal system is one of the seven lattice point groups, named after the two-dimensional rhombus. A crystal system is described by three basis vectors.
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