Quartz is a mineral composed of silicon and oxygen atoms in a
continuous framework of SiO4 silicon–oxygen tetrahedra, with each
oxygen being shared between two tetrahedra, giving an overall chemical
formula of SiO2.
Quartz is the second most abundant mineral in Earth's
continental crust, behind feldspar.
Quartz crystals are chiral, and exist in two forms, the normal
α-quartz and the high-temperature β-quartz. The transformation from
α-quartz to β-quartz takes place abruptly at 573 °C
(846 K). Since the transformation is accompanied by a significant
change in volume, it can easily induce fracturing of ceramics or rocks
passing through this temperature limit.
There are many different varieties of quartz, several of which are
semi-precious gemstones. Since antiquity, varieties of quartz have
been the most commonly used minerals in the making of jewelry and
hardstone carvings, especially in Eurasia.
Crystal habit and structure
3 Varieties (according to microstructure)
4 Varieties (according to color)
4.2 Blue quartz
4.5 Milky quartz
4.6 Rose quartz
4.7 Smoky quartz
5 Synthetic and artificial treatments
7 Related silica minerals
10 See also
12 External links
The word "quartz" is derived from the German word "Quarz", which had
the same form in the first half of the 14th century in Middle High
German in East Central German and which came from the Polish
dialect term kwardy, which corresponds to the Czech term tvrdý
The Ancient Greeks referred to quartz as κρύσταλλος
(krustallos) derived from the
Ancient Greek κρύος (kruos) meaning
"icy cold", because some philosophers (including Theophrastus)
apparently believed the mineral to be a form of supercooled ice.
Today, the term rock crystal is sometimes used as an alternative name
for the purest form of quartz.
Crystal habit and structure
Quartz mineral embedded in limestone (top right of the sample), easily
identifiable by its hexagonal form. It cannot be scratched by steel
(see Mohs scale).
Quartz belongs to the trigonal 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 (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. Well-formed crystals typically form in a 'bed' that has
unconstrained growth into a void; usually the crystals are attached at
the other end to a matrix and only one termination pyramid is present.
However, doubly terminated crystals do occur where they develop freely
without attachment, for instance within gypsum. A quartz geode is such
a situation where the void is approximately spherical in shape, lined
with a bed of crystals pointing inward.
α-quartz crystallizes in the trigonal crystal system, space group
P3121 or P3221 depending on the chirality. β-quartz belongs to the
hexagonal system, space group P6222 and P6422, respectively. 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 change in the way they
Crystal structure of α-quartz (red balls are oxygen, grey are
Varieties (according to microstructure)
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.
Major varieties of quartz
Color & Description
Zones of purple and yellow or orange
Pink, may display diasterism
Cryptocrystalline quartz and moganite mixture.
The term is generally only used for white or lightly
colored material. Otherwise more specific names are used.
Reddish orange chalcedony
Chalcedony with small inclusions (usually mica) that shimmer
Multi-colored, banded chalcedony
Semi-translucent to translucent
Agate where the bands are straight, parallel and consistent in size.
Cryptocrystalline quartz, typically red to brown
White, may display diasterism
Translucent to opaque
Brown to gray
Fibrous gold to red-brown colored quartz, exhibiting chatoyancy.
Yellow to reddish orange to brown, greenish yellow
Contains acicular (needle-like) inclusions of rutile
Contains large amounts of dumortierite crystals
Varieties (according to color)
Quartz crystal demonstrating transparency
Pure quartz, traditionally called rock crystal or clear quartz, is
colorless and transparent or translucent, and has often been used for
hardstone carvings, such as the Lothair Crystal. Common colored
varieties include citrine, rose quartz, amethyst, smoky quartz, milky
quartz, and others.
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). The cryptocrystalline
varieties are either translucent or mostly opaque, while the
transparent varieties tend to be macrocrystalline.
Chalcedony is a
cryptocrystalline form of silica consisting of fine intergrowths of
both quartz, and its monoclinic polymorph moganite. Other opaque
gemstone varieties of quartz, or mixed rocks including quartz, often
including contrasting bands or patterns of color, are agate, carnelian
or sard, onyx, heliotrope, and jasper.
Amethyst is a form of quartz that ranges from a bright to dark or dull
purple color. The world's largest deposits of amethysts can be found
in Brazil, Mexico, Uruguay, Russia, France, Namibia and Morocco.
Sometimes amethyst and citrine are found growing in the same crystal.
It is then referred to as ametrine. An amethyst is formed when there
is iron in the area where it was formed.
Blue quartz contains inclusions of fibrous magnesio-riebeckite or
Inclusions of the mineral dumortierite within quartz pieces often
result in silky-appearing splotches with a blue hue, shades giving off
purple and/or grey colors additionally being found. "Dumortierite
quartz" (sometimes called "blue quartz") will sometimes feature
contrasting light and dark color zones across the material.
Interest in the certain quality forms of blue quartz as a collectible
gemstone particularly arises in India and in the United States.
Citrine is a variety of quartz whose color ranges from a pale yellow
to brown due to ferric impurities. Natural citrines are rare; most
commercial citrines are heat-treated amethysts or smoky quartzes.
However, a heat-treated amethyst will have small lines in the crystal,
as opposed to a natural citrine's cloudy or smokey appearance. It is
nearly impossible to differentiate between cut citrine and yellow
topaz visually, but they differ in hardness.
Brazil is the leading
producer of citrine, with much of its production coming from the state
of Rio Grande do Sul. The name is derived from the Latin word citrina
which means "yellow" and is also the origin of the word "citron".
Sometimes citrine and amethyst can be found together in the same
crystal, which is then referred to as ametrine. Citrine has been
referred to as the "merchant's stone" or "money stone", due to a
superstition that it would bring prosperity.
Citrine was first appreciated as a golden-yellow gemstone in Greece
between 300 and 150 BC, during the Hellenistic Age. The yellow quartz
was used prior to that to decorate jewelry and tools but it was not
Milk quartz or milky quartz is the most common variety of crystalline
quartz. The white color is caused by minute fluid inclusions of gas,
liquid, or both, trapped during crystal formation, making it of
little value for optical and quality gemstone applications.
Rose quartz is a type of quartz which exhibits a pale pink to rose red
hue. The color is usually considered as due to trace amounts of
titanium, iron, or manganese, in the material. Some rose quartz
contains microscopic rutile needles which produces an asterism in
transmitted light. Recent X-ray diffraction studies suggest that the
color is due to thin microscopic fibers of possibly dumortierite
within the quartz.
Additionally, there is a rare type of pink quartz (also frequently
called crystalline rose quartz) with color that is thought to be
caused by trace amounts of phosphate or aluminium. The color in
crystals is apparently photosensitive and subject to fading. The first
crystals were found in a pegmatite found near Rumford, Maine, USA and
in Minas Gerais, Brazil.
Smoky quartz is a gray, translucent version of quartz. It ranges in
clarity from almost complete transparency to a brownish-gray crystal
that is almost opaque. Some can also be black. The translucency
results from natural irradiation creating free silicon within the
Not to be confused with Praseolite.
Prasiolite, also known as vermarine, is a variety of quartz that is
green in color. Since 1950, almost all natural prasiolite has come
from a small Brazilian mine, but it is also seen in
Lower Silesia in
Poland. Naturally occurring prasiolite is also found in the Thunder
Bay area of Canada. It is a rare mineral in nature; most green quartz
is heat-treated amethyst.
Synthetic and artificial treatments
A synthetic quartz crystal grown by the hydrothermal method, about
19 cm long and weighing about 127 grams
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.
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
Carnelian is widely heat-treated to deepen its
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; emeralds are also
synthesized in this fashion.
Like other crystals, quartz may be coated with metal vapors to give it
an attractive sheen.
Granite rock in the cliff of Gros la Tête – Aride Island,
Seychelles. The thin (1-3 cm wide) brighter layers are quartz veins,
formed during the late stages of crystallization of granitic magmas.
They are sometimes called “hydrothermal veins”.
Quartz is a defining constituent of granite and other felsic igneous
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.
Quartz has the lowest potential for
weathering in the
Goldich dissolution series
Goldich dissolution series and consequently it is
very common as a residual mineral in stream sediments and residual
While the majority of quartz crystallizes from molten magma, much
quartz also chemically precipitates from hot hydrothermal veins as
gangue, sometimes with ore minerals like gold, silver and copper.
Large crystals of quartz are found in magmatic pegmatites. Well-formed
crystals may reach several meters in length and weigh hundreds of
Naturally occurring quartz crystals of extremely high purity,
necessary for the crucibles and other equipment used for growing
silicon wafers in the semiconductor industry, are expensive and rare.
A major mining location for high purity quartz is the Spruce Pine Gem
Mine in Spruce Pine, North Carolina, United States.
also be found in Caldoveiro Peak, in Asturias, Spain.
The largest documented single crystal of quartz was found near
Itapore, Goiaz, Brazil; it measured approximately 6.1×1.5×1.5 m
and weighed more than 44 tonnes.
Related silica minerals
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. Lechatelierite
is an amorphous silica glass SiO2 which is formed by lightning strikes
in quartz sand.
Fatimid ewer in carved rock crystal (clear quartz) with gold lid, c.
The word "quartz" comes from the German
Quarz (help·info), which is of Slavic origin (Czech
miners called it křemen). Other sources attribute the word's origin
to the Saxon word Querkluftertz, meaning cross-vein ore.
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,
Carrowmore in Ireland. The Irish word for quartz
is grianchloch, which means 'sunstone'.
Quartz was also used in
Prehistoric Ireland, as well as many other countries, for stone tools;
both vein quartz and rock crystal were knapped as part of the lithic
technology of the prehistoric peoples.
While jade has been since earliest times the most prized semi-precious
stone for carving in
East Asia and Pre-Columbian America, in Europe
and the Middle East the 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 objects that
were very highly valued 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.
Rock crystal jug with cut festoon decoration by
Milan workshop from
the second half of the 16th century, National Museum in Warsaw. The
city of Milan, apart from
Prague and Florence, was the main
Renaissance centre for crystal cutting.
Pliny the Elder
Pliny the Elder believed quartz to be water ice,
permanently frozen after great lengths of time. (The word
"crystal" comes from the Greek word κρύσταλλος, "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. This idea
persisted until at least the 17th century. He also knew of the ability
of quartz to split light into a spectrum.
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 joined at a
perfect 60° angle.
Quartz's piezoelectric properties were discovered by Jacques and
Pierre Curie in 1880. The quartz oscillator or resonator was
first developed by
Walter Guyton Cady in 1921. George
Washington Pierce designed and patented quartz crystal oscillators in
1923. Warren Marrison created the first quartz oscillator
clock based on the work of Cady and Pierce in 1927.
Efforts to synthesize quartz began in the mid nineteenth century as
scientists attempted to create minerals under laboratory conditions
that mimicked the conditions in which the minerals formed in nature:
Karl Emil von Schafhäutl
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. However, the quality and
size of the crystals that were produced by these early efforts were
Synthetic quartz crystals produced in the autoclave shown in Western
Electric's pilot hydrothermal quartz plant in 1959
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 the 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. 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. (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 to date. 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.
Some types of quartz crystals have piezoelectric properties; they
develop an electric potential 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 a
familiar device using the mineral. 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
List of minerals
Quartz reef mining
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Karl Emil von Schafhäutl
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OCLC 1478717. 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
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^ 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
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Wikimedia Commons has media related to Quartz.
Wikisource has original text related to this article:
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Arkansas quartz, Rockhounding Arkansas
Gilbert Hart Nomenclature of Silica, American Mineralogist, Volume 12,
pages 383–395, 1927
Quartz Watch – Inventors". The Lemelson Center, National
Museum of American History. Smithsonian Institution. Archived from the
original on 7 January 2009.
Terminology used to describe the characteristics of
when used as oscillators
Quartz use as prehistoric stone tool raw material
Repoussé and chasing
Wire wrapped jewelry
Precious metal alloys
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