quartz

colorless glass made of almost pure silica a hard glossy mineral consisting of silicon dioxide in crystal form

present in most rocks (especially sandstone and granite)

yellow sand is quartz with iron oxide impurities

: ''For other senses of this word, see quartz (disambiguation)''. Quartz is the most abundant mineral in the Earth's continental crust. It has a hexagonal (crystal system)hexagonal crystal structure made of trigonal crystallized silica (silicon dioxide, SiO₂), with a hardness of 7 on the Mohs scale. Density is 2.6 g/cm³. The crystal habittypical shape is a six-sided prism (geometry)prism that ends in six-sided pyramids, although these are often Crystal twinningtwinned, distorted, or so massive that only part of the shape is apparent from a mined specimen. Additionally a ''bed'' is a common form, particularly for varieties such as amethyst, where the crystals grow up from a matrix and thus only one termination pyramid is present. A quartz geode consists of a hollow rock (usually with an approximately spherical shape) with a core lined with a bed of crystals.

Varieties - Quartz is one of the world's most common crustal minerals and goes by a bewildering 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 colour of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Colour is a secondary identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties. This does not always hold true.Not all varieties of quartz are naturally occurring. Prasiolite, an olive coloured material, is produced by heat treatment. Although citrine occurs naturally, the majority is the result of heat-treated amethyst. Carnelian is widely heat-treated to deepen its colour. ]]Because natural quartz is so often crystal twinningtwinned, 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 metres in length and massweigh hundreds of kilograms. 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 rockmetamorphic rocks.Some quartz crystal structures are piezoelectric and are used as oscillators in electronic devices such as quartz clocks and radios.A amorphous (glass) SiO₂, called lechatelierite, is caused by lightning strikes in sand, distinct from typical window glass that is impure.

History - The name "quartz" comes from the German "Quarz", which is of Slavic origin.Quartz is the most common material identified as the mystical substance maban in Australian Aboriginal mythology.Roman naturalist Pliny the Elder believed quartz to be permanently frozen ice. He supported this idea by saying that quartz is found near glaciers in the Alps and that large quartz crystals were fashioned into spheres to cool the hands. He also knew of ability of quartz to split light into a spectrum.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.

Piezoelectricity - Quartz is also a type of piezoelectric crystal that creates electricity through a process called piezoelectricity when mechanical stress is put upon it. One of the earliest uses for a quartz crystal was a phonograph pickup. Today, one of the most ubiquitous piezoelectric uses of quartz is as a crystal oscillator -- in fact these oscillators are often simply called "quartzes".

See also -

Fused quartz

list of minerals

References and external links - CommonsQuartz

Hurlbut, Cornelius S.; Klein, Cornelis, 1985, ''Manual of Mineralogy,'' 20th ed., ISBN 0471805807

mineral.galleries.com - Quartz group - Mineral Galleries

mineral.galleries.com - Quartz - Mineral Galleries

minerals.net - Quartz - Mineral.net

rockhoundingar.com - Arkansas quartz

minsocam.org - Nomenclature of !SilicaCategory:MineralsCategor y:Quartz? !varietiesar:مروca:Quarscs:K řemenda:Kvartsde:Quarzet:Kvar tses:Cuarzoeo:Kvarcofr:Quartzi t:Quarzohe:קוורץlt:Kvarca shu:Kvarcnl:Kwartsja:石英nn: Kvartspl:Kwarcpt:Quartzoro:Cua rţru:Кварцsk:Kremeňsv:K vartszh:石英

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