Quartz crystal group from Arkansas
Silica (silicon dioxide, SiO2)
ColorClear (if no impurities); also see Varieties
Crystal habit6-sided prism ending in 6-sided pyramid (typical)
rhombohedral class 32
TwinningDauphine law, Brazil law and Japan law
Mohs Scale hardness7 - lower in impure varieties
Refractive indexnω = 1.543 - 1.545 nε = 1.552 - 1.554
Optical PropertiesUniaxial (+)
Birefringence+0.009 (B-G interval)
Specific gravity2.65 constant; variable in impure varieties
Melting point1650 (±75) °C
SolubilityH2O insoluble
DiaphaneityTransparent to translucent
Other CharacteristicsPiezoelectric

Quartz (from German Quartz [1]) is the second most common density of 2.65 g/cm³.

Crystal habit

Quartz belongs to the geode is such a situation where the void is approximately spherical in shape, lined with a bed of crystals pointing inward.


Pure quartz is colorless or white, colored varieties include rose quartz, amethyst, smoky quartz and others. 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 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.

Major Varieties
Chalcedony Any cryptocrystalline quartz, although generally only used for white or lightly colored material. Otherwise more specific names are used.
Agate Multi-colored, banded chalcedony, semi-translucent to translucent
Onyx Agate where the bands are straight, parallel and consistent in size.
Jasper Opaque chalcedony, typically red to brown
Aventurine Translucent chalcedony with small inclusions (usually mica) that shimmer.
Rock crystal Clear, colorless
Amethyst Purple, transparent
Citrine Yellow to reddish orange to brown, greenish yellow
Prasiolite Mint green, transparent
Rutilated quartz Contains acicular (needles) inclusions of rutile
Milk quartz White, translucent to opaque, may display diasterism
Smoky quartz Brown to grey, opaque
Morion Dark-brown, opaque
Carnelian Reddish orange chalcedony, translucent

Synthetic and artificial treatments

  Not all varieties of quartz are naturally occurring. Carnelian is widely heat-treated to deepen its color.

Due to natural quartz being so often silicon dioxide.


Quartz occurs in hydrothermal veins and 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 metamorphic rocks.

Related silica minerals

amorphous silica glass SiO2 which is formed by lightning strikes in quartz sand.


  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 Republic of 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, Ohio, United States. This initiated the transition from mined and cut quartz for electrical appliances to manufactured quartz.

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 [2]. George Washington Pierce designed and patented quartz crystal oscillators in 1923 [3]. Warren Marrison created the first quartz oscillator clock based on the work of Cady and Pierce in 1927 [4].

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.


Quartz crystals have piezoelectric properties, that is 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 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

Wikisource has original text related to this article:


  • Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., ISBN 0-471-80580-7
  • Quartz varieties, properties, crystal morphology. Photos and illustrations
  • Arkansas quartz, Rockhounding Arkansas
  • Gilbert Hart Nomenclature of Silica, American Mineralogist, Volume 12, pages 383-395, 1927
  • Mindat.org
  • Queensland University of Technology Origin of the word quartz.
  • PDF of Charles Sawyer's cultured quartz process description
  • Smithsonian Institute, Inventors of quartz oscillating devices
  • http://www.webmineral.com/data/Quartz.shtml
  • http://www.gemstone.org/gem-by-gem/english/quartz.html
  • http://mineral.galleries.com/minerals/silicate/quartz/quartz.htm
  • http://mineral.galleries.com/minerals/gemstone/rock_cry/rock_cry.htm
  • Terminology used to describe the characteristics of Quartz Crystals when used as oscillators
  1. ^ [1]
  2. ^ Mineral Atlas, Queensland University of Technology
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