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Beautiful Quartz Cluster

The Mineral quartz




Quartz is one of the most well-known minerals on earth. It occurs in basically all mineral environments, and is the important constituent of many rocks. Quartz is also the most varied of all minerals, occurring in all different forms, habits, and colors. There are more variety names given to Quartz than any other mineral. Although the Feldspars as a group are more prevalent than Quartz, as an individual mineral Quartz is the most common mineral.

Most mineral reference guides list Chalcedony as an individual mineral, but in reality it is a variety of Quartz. It is the microcrystalline form of Quartz, forming only occurs in microscopic, compacted crystals. This page deals only with the crystalline forms of Quartz. Chalcedony is listed on its own dedicated page in this guide. Other important varieties of Quartz, such as Amethyst, Citrine, and Agate, also have dedicated pages due to their popularity and varieties.

Some forms of Quartz, especially the gemstone forms, have their color enhanced. Almost all forms of the yellow-brown variety Citrine are in fact heat treated. Much Amethyst is also heat treated to intensify color, and a green transparent form known as "Green Amethyst" or "Prasiolite" is formed by heat treating certain types of Amethyst. There is also a transparent sky blue form of Quartz crystals, as well as a wildly iridescent type that are synthetically colored by irradiation of gold. In some localities, Hematite forms a thin red or brown layer internally in the Quartz crystal, giving it a natural bright red to brown coloring, and sometimes even a mild natural iridescence.

Quartz frequently forms the inner lining of geodes. Most geodes have an inner layer of larger crystalline Quartz, and an outer layer of Chalcedony or banded Agate.

For additional information, see the gemstone section on Quartz.
Chemical Formula SiO2
Composition Silicon dioxide
Color Colorless, white, purple, pink, brown, and black. Also gray, green, orange, yellow, blue, and red. Sometimes multicolored or banded.
Streak White
Hardness 7
Crystal System Hexagonal
3D Crystal Atlas
(Click for animated model) 
Crystal Forms
and Aggregates
Crystals, which are hexagonal in shape, vary in shape and size. Quartz crystals are unique and very identifiable with their pointed and often uneven terminations. Crystals can be in enormous prismatic and stubby crystals, or in pointed aggregates of such crystals. Crystals are usually striated horizontally, and are sometimes doubly terminated. Quartz crystal habits include drusy, grainy, bladed, as linings of geodes, as rounded waterworn pebbles, radiating, as pointy pyramids on a matrix, as dense agglomerations of small crystals, massive, globular, stalactitic, crusty, in nodules, and in amygdules.

Crystals frequently twin; a famous twinning habit is the Japanese twin, where two crystals contact at a 90º angle. Quartz crystals may also contain a scepter growth, where the top of a crystal bulges out from the rest of the crystal, and may also form as phantom growth, where one crystal forms over another, leaving a ghosted form inside.

The crystal structure of Quartz is a very complicated. As a result of a changeover from alpha to beta Quartz, crystals form as hexagonal prisms with modified crystal faces.
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for a detailed explanation on the crystal structure of Quartz.
Transparency Transparent to opaque
Specific Gravity 2.6 - 2.7
Luster Vitreous. Transparent, colorless Quartz crystals from a few distinct localities may be adamantine.
Cleavage Indiscernible. Seldom exhibits parting.
Fracture Conchoidal
Tenacity Brittle
Other ID Marks 1) Some specimens fluoresce, especially white and green.
2) Triboluminescent.
3) Piezoelectric.
Complex Tests Dissolves in hydrofluoric acid
In Group Silicates; Tectosilicates; Silica Group
Striking Features Hardness, crystal forms, striations on crystal faces, and frequent appearance of conchoidal fractures on crystal faces.
Environment Quartz occurs in almost every single mineral environment.
Rock Type Igneous, Sedimentary, Metamorphic
Popularity (1-4) 1
Prevalence (1-3) 1
Demand (1-3) 1

Quartz ON EBAY
OTHER NAMES
Alpha Quartz Describes Quartz that is stable at normal room conditions.
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for more information about the crystal structure of Quartz.
Crystalline Quartz Describes any form of Quartz that forms in visible crystals, excluding the Chalcedony variety in which the crystals are microcrystalline and not visible.
Silica Describes any member of the Quartz Group, including Quartz, Chalcedony, and Opal.

VARIETIES
Varieties for Amethyst, Citrine, and Chalcedony are listed separately.
 -  Purple variety of Quartz. For additional information, see the mineral page on Amethyst.
 -  Quartz synthetically enhanced with a coating using gold (and sometimes other metals) to give it a neon blue or other neon color.
 -  Opaque form of compact Quartz or Chalcedony containing small Mica, Hematite, or Goethite scales which cause a glistening effect. Although technically Aventurine is classified as rock due to its composition of several minerals, it most often is regarded as a variety of Quartz or Chalcedony. For additional information, see the gemstone page on Aventurine.
 -  The blue variety of Quartz, which is very uncommon in nature and rarely in crystal form. Most "Blue Quartz" is what is popularly known as "Aqua Aura", essentially clear Rock Crystal synthetically irradiated with gold to form a deep sky blue color. Blue Quartz may also refer to a dull grayish-blue Quartz in massive form with Crocidolite inclusions.
 -  Form of Quartz, usually Amethyst, Citrine, or a combination of the two, that contains a large crystal or crystals overgrown with a layer of spiky smaller crystals. Cactus Quartz is specific to Boekenhoutshoek (Magaliesberg) in South Africa.
 -  Microcrystalline form of Quartz. For additional information, see the mineral page on Chalcedony.
 -  Yellow, orange, or brown variety of Quartz. For additional information, see the mineral page on Citrine.
 -  Group of Quartz crystals with a white thread-like zone running through the interior, with the crystals having formed around the thread axis.
 -  Quartz with an opaque red to brown Hematite coating or internal inclusion.
 -  Exceptionally lustrous and clear Quartz crystals from the Herkimer Co. vicinity in the Mohawk Valley region of Central New York State. Herkimer Diamond crystals are usually doubly terminated and short.
 -  White, translucent to opaque variety of Quartz.
 -  Opaque form of black Quartz. A type of Smoky Quartz.
 -  Quartz containing internal phantom growths, or ghostlike layers within a crystal.
 -  Light to emerald green, transparent to translucent Quartz, with coloring caused from inclusions of green minerals, such as Actinolite, Hedenbergite, Chlorite, or Malachite.
 -  Light green, translucent form of Quartz with Hedenbergite inclusions found on Serifos Island, Greece.
 -  Prasiolite describes a light green Quartz artificially colored by heat treatment of certain types of Amethyst. May also be called Green Amethyst by some jewelers.
 -  Quartz synthetically colored with an iridescent layer formed from gold or other metals. Also see Aqua Aura.
 -  Colorless, transparent variety of Quartz in large crystal form.
 -  Pink variety of Quartz. For additional information, see the gemstone page on Rose Quartz.
 -  Quartz with golden yellow, needle-like Rutile inclusions. For additional information, see the gemstone page on Rutilated Quartz.
 -  Quartz crystal with a scepter like protrusion on the end of the crystal that is wider than the rest of the crystal.
 -  Brown to black, "smoky" variety of Quartz. For additional information, see the gemstone page on Smoky Quartz.
 -  Polished Quartz displaying asterism in the form of a six-rayed star.
POLYMORPHS
Tridymite, Cristobalite, Stishovite, Coesite

USES
Quartz is an important mineral with numerous uses. Sand, which is composed of tiny Quartz pebbles, is the primary ingredient for the manufacture of glass. Transparent Rock Crystal has many electronic uses; it is used as oscillators in radios, watches, and pressure gauges, and in the study of optics. Quartz is also used as an abrasive for sandblasting, grinding glass, and cutting soft stones. It is also essential in the computer industry, as the important silicon semiconductors are made from Quartz.

In addition to all the practical uses, Quartz is essential to the gem trade. (See the separate Quartz gemstone page.) Many varieties are faceted as gems. Amethyst and Citrine are the most well-known gem varieties. Rose Quartz, Smoky Quartz, Rock Crystal, and Aventurine are also cut or polished into gems. Small colorless Quartz crystals are worn by some as pendants for good luck.

Quartz is also a very popular among collectors. Certain collectors specialize their collection entirely on Quartz alone.

NOTEWORTHY LOCALITIES
Excellent Quartz specimens come from numerous localities on all the corners of the globe. Only a few select localities are mentioned here. Some of the largest crystals, weighing many tons and yet still perfectly formed, come from several pegmatite mines in the state of Minas Gerais, Brazil. A very well known French locality of excellent Rock Crystal clusters is Bourg d'Oisans in Isere, especially at the La Gardette Mine.

In the U.S., flawless Rock Crystal of exceptional quality and abundance comes from Arkansas, most notably in the Hot Springs area, Garland Co.; Mount Ida in the Ouachita Mountains, Montgomery Co.; and the Jeffrey Quarry, Pulaski Co. Very large crystals also come from the pegmatite mines in the San Diego Co., California. Lustrous, doubly terminated stubby crystals come from Middleville and Little Falls, Herkimer Co.; and St. Johnsville, Montgomery Co., New York, where they are known affectionately as Herkimer Diamonds.

Although Rose Quartz is very common, good crystals are rare and only found in a handful of localities. These are mostly in Minas Gerais, Brazil, in Galileia (especially at Lavra da Pitorra); and in Itinga, in the Jequitinhonha Valley; and also at Newry, Oxford Co., Maine.

Fine Smoky Quartz comes from the Pikes Peak area, El Paso Co., Colorado. The Alps contain two very classic occurrences in Switzerland in St. Gotthard, Uri, Switzerland; and in Chamonix-Mont Blanc, France. The finest Rutilated Quartz comes from Novo Horizonte and Ibitiara, Bahia, Brazil. Tall prismatic Quartz colored dark green from Hedenbergite inclusions come from Serifos Island, Greece. Exceptional Faden Quartz comes from the Dara Ismael Khan District, Waziristan, Pakistan.

COMMON MINERAL ASSOCIATIONS
Quartz occurs in virtually all mineral environments, and may be associated with almost every mineral.

DISTINGUISHING SIMILAR MINERALS
Beryl - harder (7½ - 8), lacks horizontal striations.
Feldspars - Softer (6), perfect cleavage.
Calcite - Much softer (3).


quartz PHOTOS
Images for the varieties Amethyst, Citrine, and Chalcedony are listed separately.
 
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