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Quartz Brésil.jpg
Pure quartz (rock crystal)
General and classification
other names
  • α-quartz
  • Deep quartz
chemical formula SiO 2
Mineral class
(and possibly department)
Oxides with metal: oxygen = 1: 2 (and comparable) - with small cations: silica family
System no. to Strunz
and to Dana
4.DA.05 ( 8th edition : IV / D.01)
Similar minerals no
Crystallographic Data
Crystal system trigonal
Crystal class ; symbol trigonal trapezoidal; 32
Space group P 3 1 21 (No. 152) and P 3 2 21 (No. 154)Template: room group / 152Template: room group / 154
Lattice parameters a  = 4.9124  Å ; c  = 5.4039 Å
Formula units Z  = 3
Frequent crystal faces {10 1 1}, {01 1 1}, {10 1 0}
Twinning predominantly complementary twins
Physical Properties
Mohs hardness 7th
Density (g / cm 3 ) 2.65
Cleavage no
Break ; Tenacity clamshell; brittle
colour colorless, white, all colors possible
Line color White
transparency transparent to opaque
shine Glass gloss on prismatic surfaces ,
fat gloss on fractured surfaces
Crystal optics
Refractive indices n ω  = 1.543
n ε  = 1.552 (each at 633 nm)
Birefringence δ = 0.0091
Optical character positive
Axis angle 2V = more often anomalous with 2v z ~ 0 to 10 °
Pleochroism is missing
Other properties
Chemical behavior chemically extremely inert, reaction only with hydrofluoric acid and soda - melts
Special features may contain fluid inclusions

Quartz , also known as deep quartz or α-quartz , is a mineral with the chemical composition SiO 2 and trigonal symmetry . It is the stable form ( modification ) of silicon dioxide on the earth's surface and, after the feldspars, the second most common mineral in the earth's crust. At a temperature of over 573 ° C (under a pressure of 1 bar), deep quartz changes to high quartz due to a change in the crystal structure .

With a Mohs hardness of 7, quartz is one of the hard minerals and serves as a reference value on the Friedrich Mohs scale, which goes up to 10 ( diamond ) . It often forms well-developed crystals of a great variety of shapes and colors , the crystal surfaces of which have a glass luster . Quartz has no cleavage , breaking muschelig as glass and displays on the fracture surfaces a greasy shine .

In the industry Quartz is one of the most important minerals and has equally as a building material such as raw material for ceramic - glass - and cement industry worldwide importance. Quartz gravel and broken quartz are raw materials for the extraction of silicon .

In addition, quartz and its colored varieties have long been valued as a gemstone (see use ).

Quartz crystals are also produced artificially: oscillating quartz crystals cut from them serve as clock generators in electronic circuits and quartz watches .

Occasionally, quartz is confused with calcite , but can easily be distinguished from it by its greater hardness, lower birefringence and the reaction of calcite with dilute hydrochloric acid .

Etymology and history

Quartz sand from Coral Pink Sand Dunes State Park , Utah; the orange color is caused by the hematite layer .

The expression is first attested in the first half of the 14th century in East Central German as a technical term of the Bohemian mining ( quartz ). There are various hypotheses about its origin. According to one of these hypotheses, it comes from mhd. Querch (' dwarf ') based on the superstition that mountain spirits underlay the minerals that are worthless from a mining point of view after they have “stolen” a valuable ore originally present in the same place (cf. also the etymology of Cobalt ). Another hypothesis is that quartz comes from kwardy , an expression from a Polish dialect, which corresponds to the Czech word tvrdý ('hard'). According to a hypothesis by Sergei Iwanowitsch Tomkeieff from 1942, the word is supposed to be a contraction of the Saxon miner's expression "Querklufterz". Tomkeieff assumes the form quertz, querz as the basic form, which can be found in writings from the 16th century such as A useful Bergbüchlin and Agricolas De re metallica with reference to the language used by Saxon miners. However, in the seventh volume of Grimm's dictionary published in 1889, similar derivations, which have existed since the 16th century and which assume a contraction of quaterz, quaderz ('bad ore') or from warz, gewärze ( collective term for wart ), are described as “ gambling attempts to fathom the origin of the word ”.

Quartz has established itself internationally as a mineral name, with slight, language-specific modifications such as quartz in English and French , kvarts in Swedish , quarzo in Italian or кварц (kwarz) in Russian .


According to the 8th and 9th edition of Strunz's system of minerals, quartz belongs to the mineral class of oxides with a metal-oxygen ratio of 1: 2 due to its chemical composition .

In the 8th edition of the mineral systematics , he is also the namesake for a group of chemically similar or identical minerals, the quartz group , the other members of which are coesite , cristobalite , melanophlogite , mogánite , opal , stishovite and tridymite .

The 9th edition of the mineral classification according to Strunz, however, subdivides the oxides more finely. Quartz as well as the related minerals beta-quartz (existence previously only known as a synthesis) coesite, cristobalite, melanophlogite, mogánite, seifertite , opal, stishovite and tridymite are now assigned to the subdivision (chemical compounds) with small cations : silica family . The lechatelierite (silica glass) also listed in the system , however, still has a questionable mineral status and is therefore not recognized as an independent mineral by the International Mineralogical Association (IMA).

The system of James Dana arranges the minerals according to their crystal structure . In quartz, silicon is tetrahedrally surrounded by four oxygen atoms. These SiO 4 tetrahedra are linked at their corners to form a three-dimensional framework, and quartz is therefore assigned to the framework silicates in Dana’s system.


Quartz is a very pure compound and only incorporates traces of other elements into the crystal lattice . Natural quartz can contain between 13 and 15,000  ppm (but mostly only a few 100 ppm) Al 3+ , between 9 and 1400 ppm Na + , between 3 and 300 ppm K + , as well as smaller amounts of Fe 3+ , Ti 4+ , P 5 + , H + and Li + included.

These ions are usually incorporated via a coupled replacement (substitution) of a Si 4+ ion by a trivalent and a monovalent ion, such as Al 3+ and Na + . The foreign ions are built into the Si positions in the lattice as well as in otherwise empty interstitial spaces. In addition to the inclusion of foreign minerals, the incorporation of metal ions, partly in conjunction with ionizing radiation , is responsible for the different colors of the quartz varieties.

Crystal structure

Deep quartz is trigonal trapezoidal ( crystal class 32) and crystallizes in the enantiomorphic space groups P 3 1 21 (no. 152) and P 3 2 21 (no. 154) . The dimensions of the unit cell are a 1  = a 2  = 4.9124  Å and c = 5.4039 Å. A unit cell contains three formula units SiO 2 . Silicon (Si) and oxygen (O) occupy crystallographically distinguishable atomic positions: Template: room group / 152Template: room group / 154

  • Si: x = 0.4701; y = 0; z = 1/3
  • O: x = 0.4139; y = 0.2674; z = 0.2144

Each oxygen ion is surrounded by two silicon ions 1.6054 Å and 1.6109 Å apart, and six oxygen ions about 2.62 Å apart. The Si-O bonds have a large covalent content, which is the reason for the great hardness of quartz. The Si-O-Si bond angle is 143.61 °. Accordingly, each silicon ion is tetrahedrally surrounded by four oxygen ions, two at a distance of 1.6054 Å and two at a distance of 1.6109 Å.

SiO 2 framework : The SiO 4 tetrahedra are linked to one another via the tetrahedron corners , each tetrahedron with four neighboring tetrahedra. In the direction of the c-axis they are linked to form pairs of spiral chains. These SiO 4 tetrahedral helix pairs, which are not connected to one another, form six-sided, open channels in the direction of the c-axis.

α-quartz crystals of the two enantiomorphic space groups differ in the direction of rotation of the tetrahedron screws. Left-handed α-quartz crystallizes in the space group P 3 1 21 (no. 152) and the tetrahedron screws turn clockwise around the c-axis towards the viewer when looking at the c-axis from above. Correspondingly, the tetrahedron screws of the right-handed α-quartz (space group P 3 2 21 (No. 154) ) wind counterclockwise towards the viewer. The spiral tetrahedron chains are linked to six neighboring tetrahedron spirals in such a way that each SiO 4 tetrahedron belongs to two neighboring tetrahedron chains and borders two of the six-sided channels. Template: room group / 152Template: room group / 154

Quartz is only stable in the trigonal α-quartz phase at low temperatures. At 573 ° C there is a phase change into the hexagonal β-quartz phase. The transition from the β-quartz phase to the α-quartz can be easily illustrated by tilting robust tetrahedra around the <100> axis. The direction of tilt determines the orientation of the α-quartz.



Left quartz morphology

Well-formed crystals are common and their shape can vary considerably depending on the growing conditions. The figure opposite illustrates the typical prismatic crystal shape of left quartz and how this shape is composed of the basic bodies of the trigonal-trapezoidal class (class 32). The numbers in brackets in the text and in the illustration are the Miller indices . They are used in crystallography to denote crystal faces. Indices of crystal faces are put in round brackets, indices of a group of faces that form a basic body in curly brackets and indices of directions (crystal axes) in square brackets.

The crystal shape is dominated by the hexagonal prism I position ({10 1 0}). The prism surfaces are parallel to the crystallographic c-axis. The prism is bounded at the ends by the positive and negative rhombohedron ({10 1 1} and {01 1 1}), with the positive main thrombohedron appearing with larger areas.

Subordinate, d. H. formed smaller, there are various trigonal trapezoids , mostly {51 6 1}, and trigonal bipyramids , mostly {11 2 1}. There are two enantiomorphic (left and right), but otherwise identical forms of these polyhedra in crystal class 32. Either only right or left trapezohedra and bipyramids occur on an untwinning quartz crystal, left forms on left quartz (space group P 3 1 21 (No. 152) ) and right forms on right quartz (space group P 3 2 21 (no. 154) ). Right and left quartz crystals can be distinguished based on the arrangement of the trapezoidal and bipyramidal surfaces. With the left quartz these occur to the left of the main thrombohedral surfaces {10 1 1} and with the right quartz to the right of the main thrombohedron surfaces. Template: room group / 152Template: room group / 154

Crystal and growth forms

Separate names have been established for conspicuous forms of growth of quartz:

  • Ticino habitus: Quartz, the crystal form of which is dominated by large, very steep rhombohedral surfaces.
  • Skeletal quartz: With rapid crystal growth in oversaturated solutions, growth occurs particularly along the crystal edges and corners. Edges that are highlighted like a frame are formed around lower crystal surfaces (frame quartz). Sometimes these deeper-lying crystal surfaces grow closed again from the protruding edges, with thin quartz disks forming over a cavity (window quartz).
  • Cap quartz : Quartz crystals in which parts at the end of the crystal can be removed like a cap.
  • Cube quartz : Quartz whose crystal form is dominated by the rhombohedral surfaces {10 1 1}. The angle between these surfaces is 85.5 ° in quartz, which gives these crystals a cubic habit .
  • Scepter quartz: If a second, young generation grows on a quartz crystal in the direction along the main axis, so-called scepter quartz form. The “daughters” are usually clearer than the mother crystal. If the later crystal growth only takes place at one end of the crystal, the characteristic, scepter-shaped crystal shape develops.
  • Filamentary quartz: A filamentary quartz is formed when a fracture occurs during crystal growth and the crystal tears apart. As the gap opens , the crystal grows back together from both sides of the crack. The crack itself remains visible as a thin “thread” in the crystal. It appears on the sanded and polished surface like sanding marks and an accumulation of fine holes in lines (stripes).
  • Friedländer Quartz: Quartz crystals with surface stripes on the surfaces of the six-sided prism (10 1 0) transversely to the crystallographic c-axis or to the prism.
  • Phantom quartz: If the crystal growth takes place in several phases, the different growth stages are visible in clear crystals through zones rich in inclusion .

Other names are common for certain intergrowths of several crystals:

  • Sprout quartz or artichoke quartz : Quartz that have formed many individual daughter crystals due to lattice defects and thus formed artichoke-shaped aggregates.
  • Coiled quartz (Gwindel): parallel intergrowth of several platy crystals along a prismatic surface, whereby the crystallographic main axes of the individual crystals are not in one plane, but are twisted against each other.

Crystal twins

Quartz twin with small hollandite tufts

The two chiral forms of quartz, right-hand quartz and left-hand quartz, sometimes also appear to be fused together in an oriented manner.

  • Brazilian twin: The Brazilian twin describes the oriented fusion of the two enantiomorphic forms of deep quartz, right and left quartz parallel to the prism surface (11 2 0). Brazilian twins are often finely lamellar and typical of amethyst. There, Brazilians find twin lamellae concentrated in the {101} rhombohedron sectors. The incorporation of traces of iron into the quartz structure appears to play an important role in the formation of the fine-lamellar Brazilian twins of amethysts. Corresponding to the concentration of the twin lamellae in the {101} rhombohedron sectors, amethysts show a higher iron concentration in these sectors. In the rare variety ametrine (two-colored quartz crystals) this sector zoning becomes visible. The sectors with less iron are purple and the areas with more iron are yellow.
  • Dauphinée twin (also Swiss or Alpine twin law ): The Dauphinée twin is the term used to describe the penetration of two deep quartz crystals with the same sense of rotation, so that the surfaces of the positive rhombohedra {h0 h l} of one crystal individual with the surfaces of the negative rhombohedra {0h h l} of the other crystal individual coincide. The twin axis is either [0001] or [10 1 1]. The pyro- and piezoelectric effects of the two crystal individuals cancel each other out. Dauphinée twins are therefore unsuitable for most technical applications.
  • Japanese twin: Twinning of deep quartz according to the dipyramid II position (11 2 2). The prism axes of the twinned crystals intersect at an angle of 84 ° 33 ', which gives the twins a characteristic, heart-shaped shape.
Japanese twin
  • Liebisch twin
  • Esterel twin: twinning according to (10 1 0)
  • Sardinia twin: twinning according to (10 1 2)
  • Belodwa beacon twin: twinning according to (30 3 2)
  • Cornish twin: twinning according to (20 2 1)
  • Wheal Coats twin: Twinning according to (21 3 1)
  • Pierre Levee twin: twinning according to (21 3 3)


Quartz shows a strong piezoelectric effect perpendicular to the prism axis along the a-axes. A quartz crystal reacts to pressure or tension with an electrical polarization along the direction of force. Conversely, the application of an electrical direct voltage leads to an expansion or compression of the crystal. If an alternating voltage with a suitable frequency is applied, the crystal can be excited to resonate . The resonance frequency depends on the geometry (shape and size) of the crystal. Due to the regularity and accuracy of these oscillations , quartz oscillators are used in quartz oscillators as a time base and clock generator for electronic circuits, for example in clocks, computers , digital technology and radio technology devices .

Optical activity

The crystallization of the quartz in an enantiomorphic structure rotates the oscillation plane of the light that traverses a deep quartz in the direction of the c-axis. The specification of exact measurement results of this rotation proves to be difficult, since measurement results vary widely due to various disruptive factors such as undetected twinning of right and left quartz or the smallest impurities. In addition, manufacturing tolerances make it more difficult to produce precisely oriented quartz cuts. Furthermore, the strength of the rotation of the plane of oscillation of the light depends on the wavelength of the light (example: sodium D line : 589.3 nm, green filter for mercury vapor lamps : 546 nm). The indication of the optical rotation capacity of quartz fluctuates between 21 and 28 ° / mm depending on the source and wavelength. On the other hand, processed quartz in the form of quartz plates is ideal for checking polarimeters .

Education and Locations

Quartz can be found in nature as such boulders ("pebbles")

Quartz is a very common mineral and can be found in numerous representatives of all three rock classes.

It crystallizes when SiO 2 -rich melts cool down and is the primary component of SiO 2 -rich plutonites ( quartz- rich granitoids , granites , granodiorites , tonalites , quartz-syenites , quartz-monzonites , quartz-diorites ) and the corresponding volcanites ( rhyolites , Dacite , Andesite , Quartz Trachyte , Quartz Latite ). The quartz content of these rocks is one of the main criteria for their classification according to the route iron diagram .

Quartz is also found in many metamorphic rocks (e.g. in horn rocks , phyllites and gneisses ). There it is either inherited from the parent rock or it is formed through countless mineral reactions during the rock metamorphosis. For example, the reaction of chloritoid and aluminosilicate to form staurolite and quartz marks the boundary between green slate facies and amphibolite facies in metapelites .

Because of its resistance to weathering, quartz is also a frequent constituent of fine-grained (but not the finest-grained) clastic sedimentary rocks (primarily: sandstones ) and of soils that have developed on quartz-rich rocks.

Well-formed quartz crystals with collector's value, on the other hand, tend to arise in crevices, hydrothermal tunnels (as so-called gangue ) and as the lining of natural cavities, so-called geodes .


Polished rock crystal pieces

Quartz is the stable form ( modification ) of crystalline silicon dioxide on the earth's surface . Numerous other modifications occur at higher pressures and temperatures. Some can remain metastable on the surface of the earth.

At low temperatures (70–200 ° C) a mixture of quartz and mogánite , a characteristic component of quartzine and chalcedony, crystallizes from SiO 2 gel .

At temperatures above 573 ° C (at 1013.2  hPa ), quartz converts to high quartz. The phase transition takes place very quickly, and high quartz never remains metastable even when it is cooled rapidly. Although quartz crystals with the crystal form of high quartz ( paramorphosis ) can be found in some igneous rocks , it is structurally quartz.

At higher temperatures, high quartz first transforms into tridymite (from 867 ° C), then into cristobalite (from 1470 ° C). Cristobalite melts at 1727 ° C (temperatures in each case based on 1013.2  hPa ).

The transformation temperatures depend on the pressure. In general, they increase with increasing pressures.

Particularly dense SiO 2 phases are formed at high pressure, such as that prevailing in the earth's mantle or when meteorite impacts occur . From 2 G Pa forms Coesite (3.01 g / cc), from 7.5 G Pa stishovite (4.3 g / cc) and from about 78 G Pa Seifertit (4.12 g / cc).


Pure quartz is completely transparent and colorless and, when it develops well-formed crystals, is called rock crystal . Quartz is usually milky due to microscopic inclusions of liquids and gases ( milk quartz ) and appear gray when grown in the rock . Under the name of rhinestone are also transparent to milky Roll pieces of rock crystal known mainly originating from the Alps and the Rhine gravel found.

Due to the incorporation of coloring ions (generally Fe 3+ or Fe 2+ ), inclusion of colored minerals or the action of ionizing radiation, quartz can be colored differently. The following varieties are distinguished based on the color and its cause:

Color variations due to foreign ions or radiation

Ametrine from Bolivia
  • Amethyst : purple color due to the interplay of embedded iron ions and irradiation with gamma rays
  • Ametrine : a rare variety of quartz that shows sectors with amethyst and citrine color on a crystal
  • Citrine : yellow to orange-brown colored quartz (also artificially produced by burning )
  • Prasiolite ( green quartz): leek- green and transparent quartz that rarely occurs naturally and is also artificially produced by firing amethyst or yellowish quartz
  • Smoky quartz ( Morion ): colored gray-brown (smoke-colored) to black (Morion) by natural or artificial gamma rays
  • Nickel quartz: coarse green quartz that is colored by nickel.

Color variations due to inclusions

Milk quartz
Rose quartz with asterism
  • Blue quartz ( sapphire quartz ): blue, opaque aggregate with embedded crocidolite fibers or dumortierite . Depending on the type of inclusion, blue quartz is more precisely referred to as crocidolite quartz or dumortierite quartz or dumortierite quartz .
  • Iron pebbles : quartz colored red-brown by hematite inclusions
  • Strawberry quartz is a variety and trade name for quartz that is irregularly pink to red in color due to red-brown hematite inclusions . It is usually more transparent and stronger in color than rose quartz.
  • Milky quartz : Milky-cloudy quartz due to inclusions of liquid
  • Prasem ( emerald quartz ): leek- green, opaque aggregate that gets its color from inclusions of actinolite .
  • Rose quartz : dumortierite inclusions, cloudy, pink colored quartz, occasionally with asterism due to the inclusion of the finest rutile needles

Microcrystalline SiO 2

Agate slice

Microcrystalline quartz is understood to mean massive aggregates of very fine crystalline quartz with crystal sizes in the micrometer range. There are three different forms:

  • Chalcedony : microcrystalline, fibrous quartz, fibrous grown along a prism surface [11-20] ("length-fast").
  • Micro quartz : microcrystalline, granular quartz without any recognizable preferred growth direction
  • Quartz : microcrystalline, fibrous quartz, fibrous grown along the base surface (0001) of the hexagonal prism ("length-slow").

Amethyst quartz is an opaque, banded intergrowth of amethyst and milk quartz.

All forms of microcrystalline quartz have a high density of lattice defects and twinning.

Chert and flint are adhesions of microcrystalline quartz with mogánite in a random, granular structure. Strictly speaking, these are not minerals and mineral varieties, but rocks, which are also summarized under the generic term chert . Chalcedony and its manifestations as well as amorphous SiO 2 ( opal ) are sometimes subsumed under this.

Other varieties and trade names

The Aqua Aura, which can often be found in stores, is not a variety, but mostly rock crystal (or another quartz) that has been vaporized with metal (mainly gold ). The result is a transparent, blue-colored crystal, sometimes with a multicolored shimmer.

Brazilite , on the other hand, is the trade name for a quartz that is greenish-yellow to pale yellow in color when it is fired. In the Safiental (Graubünden, Switzerland) the world's first finds of the mantle quartz were found, the tip of which is slightly sunk into the prism.


projectile points (approx. 3500-2500 BC, New York State). The tip on the left is made of macrocrystalline quartz, the middle and right made of flint .

Prehistory and early history

Quartz has a relatively high hardness and the property of breaking sharp-edged in the event of short-term strong mechanical stress. Therefore, this mineral in its various forms, including hornfels , quartzite and especially flint , was used as a raw material for many tools and weapons by representatives of the human species as early as the Paleolithic . Although it is more difficult to work with than flint, stone artifacts made of macrocrystalline quartz (vein quartz, even rock crystal) dominate in individual sites , provided that it is available in the immediate vicinity, especially in sub-Saharan Africa.

Preferably unprocessed quartzite nodules or raw rock were used as striking stones for stone processing. Larger chunks of macrocrystalline quartz were also preferred as cooking stones because they are less prone to bursting due to rapid temperature changes.

As a raw material

  • Quartz sand or powder, together with kaolin and feldspar, is an additive for porcelain and a large number of other ceramic materials.
  • Quartz sand or ground quartz rock is melted to produce glass and quartz glass. Quartz glass is a of (crystalline) quartz or silica erschmolzener, glassy solidified solid; the correct name is therefore silica glass. Quartz glass and also artificial quartz single crystals (pure rock crystal) are cut into optical prisms and lenses . Quartz glass is also used in standard scales and weights as well as a thread for torsion balances and as an optical fiber .
  • In addition, quartz gravel and broken quartz are raw materials for the production of silicon .

As material

Quartz and quartz glass only react with a few chemicals . Hydrofluoric acid is the only acid that can dissolve quartz, which forms silicon tetrafluoride or hexafluorosilicic acid . This property is beneficial for a large number of application areas:

  • Vessels for chemicals
  • In fluidized bed combustion , quartz sand is swirled with the air to improve heat transfer and optimize the combustion process.
  • In addition, quartz is used in the form of refractory stones.
  • Its high strength, which prevents vegetation, leads to the use of the mineral as a railway ballast body. Quartz is unsuitable as road gravel because it is too hard, binds poorly and causes car tires to wear out quickly.
  • Quartz crystal plates made of unweathered quartz are used in electroacoustics .
  • Quartz sand is used as an abrasive and filler as well as for extinguishing arcs in fuses . It is also used to make water glass and silicate paints . With polymers mixed, he also serves as a material to hard surfaces for floors and countertops to create.

Use of the piezoelectric properties

3Com OfficeConnect ADSL Wireless 11g Firewall Router 2012-10-28-0866.jpg
Piezoelektryczny rezonator kwarcowy.jpg
Above a quartz oscillator in a typical metal case (in a router ), underneath an open case with an exposed quartz disc (slightly larger design than on the picture above )
Quartz Wrist Watch (with temperature compensation for higher accuracy , manufactured by Seiko )

Artificially pulled quartz single crystals are u. a. used for piezoelectric applications. The piezoelectric properties of quartz are used in quartz oscillators which, when suitably excited by an electrical voltage, oscillate mechanically at a fixed frequency . This made it possible to build very precise quartz watches . Quartz oscillators are used as clock generators in practically all electronic devices today . In addition, quartz is also suitable for pressure measurements , in high-frequency technology and as an acousto-optical Q switch in lasers.

The two chiral forms of quartz, right quartz and left quartz, show a contrary piezoelectric effect. In such twins , therefore, the piezoelectric effects cancel each other out in the overall crystal, which is why they are useless for piezoelectric applications and are used less often than synthetic quartz crystals. For technical applications, the twins are often cut parallel to the (01-1) plane (AT section) or (023) plane (BT section), since the piezoelectric effect perpendicular to these planes is almost independent of the temperature.

As a gem

Quartz varieties such as agate , purple amethyst , lemon yellow citrine , blood red jasper or black and white striped onyx are processed into gemstones in the jewelry industry because of the great hardness and the ease with which the mineral can be cut and polished .

Quartz and fossilization

Silicified coral stock from the Tampa subformation of the Arcadia Formation (Lower Miocene of Florida)
Silicified wood from the Mesozoic era of Madagascar
Sections of agate “ stone cores ” from the Dekkan Trapp in India: here the inside of the case has been largely filled with microcrystalline quartz, while the actual case has not been preserved. This special form of conservation is also Fossilpseudomorphose called.

If silica-rich groundwater penetrates the tissue of dead woody plants, these can fossilize through the crystallization of microcrystalline quartz (Si (OH) 4 → SiO 2 + 2 H 2 O), whereby the woody tissue is replaced by quartz, the original cell structure however, it often remains. From this, paleobotanists can now draw conclusions about the plant's former growth conditions, for example. Fossilized araucaria cones from Patagonia are also known .

There is also silicification from animals. Often an exoskeleton or housing, which previously consisted of calcium carbonate (CaCO 3 ), is replaced by microcrystalline quartz. For example, silicified corals from the Miocene of Florida and the Triassic of British Columbia and Alaska, opalescent snails, mussels and vertebrate remains from the Lower Cretaceous of the Lightning Ridge in Australia and silicified snails from the Dekkan Trapp (Upper Cretaceous) in India are known. If the interior of these snails was not completely filled with sediment after the extensive decomposition of the soft tissues, agate-like drusen can also be formed in them.

Damage to health

The mining and processing of quartz can produce fine quartz dust which, if inhaled daily for months or years, can lead to silicosis, which is feared among miners and, in extreme cases, even to lung cancer .

However, it comes at the grinding of gemstones hardly generate dust because of the abrasive action always sufficiently cooled with an excess of water, emulsion, petroleum or a special grinding oil and the dust is bound. A dry cut would also damage or destroy most gemstones.


In esotericism , pure quartz (rock crystal) is considered a healing stone , which is supposed to protect against harmful rays, relieve headaches and various inflammations, cleanse the liver and kidneys and strengthen blood circulation (varicose veins).

Quartz in the rock crystal variety is assigned to the zodiac sign Leo and in the quartz cat's eye variety to the Capricorn . Alternatively, quartz or rock crystal can also be assigned to the zodiac signs Taurus, Gemini or Sagittarius . As a “month stone”, rock crystal stands for April and as a “planetary stone” according to Richardson and Huett (1989) next to the tiger's eye for Saturn and several other minerals for Neptune .

The various varieties such as the yellow citrine or the purple amethyst are also mainly attributed properties that can be derived from the mythology of their color, for example yellow for energy and purple for spirituality . Horn silica is used in biodynamic agriculture .

However, there is no scientific evidence for the listed effects.

See also


  • Friedrich Klockmann : Klockmann's textbook of mineralogy . Ed .: Paul Ramdohr , Hugo Strunz . 16th edition. Enke, Stuttgart 1978, ISBN 3-432-82986-8 , pp. 521-526 (first edition: 1891).
  • PJ Heaney, CT Prewitt, GV Gibbs (Eds.): Silica. Physical Behavior, Geochemistry and Materials Applications . Mineralogical Society of America, Washington 1994, ISBN 0-939950-35-9 .
  • Rudolf Rykart: Quartz Monograph . Ott, Thun 1995, ISBN 3-7225-6204-X .
  • Petr Korbel, Milan Novák: Mineral Encyclopedia (=  Villager Nature ). Edition Dörfler im Nebel-Verlag, Eggolsheim 2002, ISBN 978-3-89555-076-8 , p. 88-95 .

Web links

Wiktionary: Quartz  - explanations of meanings, word origins, synonyms, translations
Commons : Quartz  - collection of images, videos and audio files

Individual evidence

  1. a b c G. Will, M. Bellotto, W. Parrish, M. Hart: Crystal structures of quartz and magnesium germanate by profile analysis of synchrotron radiation high-resolution powder data . In: Journal of Applied Crystallography . tape 21 , no. 2 , April 1988, pp. 182-191 , doi : 10.1107 / S0021889887011567 .
  2. Quartz, crystalline (SiO 2 ). In: korth.de. Korth Kristalle GmbH, accessed on January 21, 2019 .
  3. a b Digital dictionary of the German language: Quarz. In: dwds.de. Berlin-Brandenburg Academy of Sciences, accessed on January 21, 2019 .
  4. a b English Oxford Living Dictionaries: quartz. In: en.oxforddictionaries.com. Oxford University Press, accessed January 21, 2019 .
  5. Sergei Ivanovich Tomkeieff: On the origin of the name 'quartz' . In: Mineralogical Magazine . tape 26 , no. 1 , 1942, p. 172–178 (English, rruff.info [PDF; 351 kB ; accessed on January 21, 2019]).
  6. " item under the silbergengen are some who yn hāgends and ligends QUERTZ have [...]." Ulrich Rülein of Calw: A useful Bergbüchlin. 4th (?) "Edition", Erfurt 1527, p. 32
  7. ^ Quartz in Grimm's Dictionary, Volume VII (N, O, P, Q), 1889, online version (Competence Center for Electronic Cataloging and Publication Processes in the Humanities, University of Trier)
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  9. ^ Walter Schumann: Precious stones and gemstones. All kinds and varieties. 1900 unique pieces . 16th revised edition. BLV Verlag, Munich 2014, ISBN 978-3-8354-1171-5 , pp. 198 .
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This version was added to the list of articles worth reading on August 14, 2007 .