quartz
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What is quartz?
Quartz is a widely distributed mineral consisting primarily of silica, or silicon dioxide (SiO2). It is the second most abundant mineral in the Earth’s crust after feldspar and appears in nearly all acid igneous, metamorphic, and sedimentary rocks.
Quartz has great economic importance. Many varieties are gemstones, including amethyst, citrine, smoky quartz, and rose quartz. Large amounts of quartz sand are used in the manufacture of glass and ceramics and for foundry molds in metal casting.
Quartz is also piezoelectric: a crystal develops positive and negative charges on alternate prism edges when subjected to pressure or tension. China, Japan, and Russia are the world’s primary producers of quartz.
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What are some common places where quartz can be found?
Quartz, a mineral composed of silicon and oxygen, is found in various environments. It is a primary component of igneous, sedimentary, and metamorphic rocks. Quartz can be found in:
- Igneous Rocks Quartz appears in magma that contains more than 47% of silica.
- Sedimentary Rocks Quartz is enriched in river, lake, and beach sediments.
- Metamorphic Terrains Quartz-bearing strata are abundant in metamorphic terrains.
- Veins Quartz precipitates along channelways from cooling igneous rocks or deep fractures.
- Lunar rocks and meteorites Quartz has also been found in meteorites and some lunar rocks.
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What are the main properties of quartz?
Quartz is a widely distributed mineral that consists primarily of silica, or silicon dioxide ((SiO_2)). It is the second most abundant mineral in Earth’s crust.
Key properties of quartz:
- Composition Quartz is primarily silica, or silicon dioxide ((SiO_2)).
- Crystal Structure Quartz crystals lack a center or planes of symmetry and have one crystallographic axis perpendicular to three polar axes.
- Hardness Quartz has a hardness of 7 on the Mohs scale and resists fracture because it lacks easy cleavage.
- Forms Quartz exists in two forms: alpha- or low quartz, which is stable up to 573 °C (1,063 °F), and beta- or high quartz, stable above 573 °C.
- ** piezoelectricity** Quartz is piezoelectric, meaning a crystal develops positive and negative charges on alternate prism edges when subjected to pressure or tension.
- Color Colored varieties of quartz are numerous and have many causes.
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How is quartz formed in nature?
Quartz, a form of silica, is created in various geological settings. It appears when there is an excess of silica (SiO2) in crystallizing magma, typically in magmas containing over 47% silica.
Quartz can also form through precipitation from gases or solutions escaping from cooling igneous rocks, resulting in veins of fine to coarse crystals. Additionally, it can develop during the metamorphism of rocks, where silica is reincorporated or redeposited. The solubility of silica minerals is influenced by temperature, pressure, and the presence of certain ions, affecting quartz formation in natural solutions.
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What are some uses of quartz in everyday life?
Quartz, a silicon dioxide mineral, has many uses in everyday life due to its unique properties.
- Gemstones Many varieties of quartz, such as amethyst, citrine, and rose quartz, are used as gemstones.
- Abrasives Crushed quartz is used as an abrasive in sandpaper and sandblasting.
- Glass and ceramics Quartz sand is used in the manufacture of glass and ceramics.
- Electronics Due to its piezoelectric properties, quartz is used for frequency control in radios, televisions, and crystal-controlled clocks and watches.
- Building stone Sandstone, which is mainly composed of quartz, is an important building stone.
- Other uses Quartz is also used to make molds for metal casting, laboratory vessels, and optical instruments.
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How does quartz differ from other common minerals, like feldspar or calcite?
Quartz, feldspar, and calcite are common minerals, but they differ significantly in their chemical composition and physical properties. Quartz is primarily composed of silica ($SiO_2$). Feldspars are aluminosilicate minerals with the general formula $AT_4O_8$, where A can be potassium, sodium, or calcium, and T is silicon and aluminum. Calcite is composed of calcium carbonate ($CaCO_3$), and some natural calcites contain other cations like magnesium, manganese, or iron.
These minerals also differ in hardness. Quartz has a Mohs hardness of 7, meaning it can scratch glass easily. Feldspar has a Mohs hardness of approximately 6. Calcite is softer, with a Mohs hardness of 3, so it can be scratched easily with a knife. Another key difference is that calcite reacts with dilute hydrochloric acid, producing effervescence, while quartz and feldspar do not.
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quartz, widely distributed mineral of many varieties that consists primarily of silica, or silicon dioxide (SiO2). Minor impurities such as lithium, sodium, potassium, and titanium may be present. Quartz has attracted attention from the earliest times; water-clear crystals were known to the ancient Greeks as krystallos—hence the name crystal, or more commonly rock crystal, applied to this variety. The name quartz is an old German word of uncertain origin first used by Georgius Agricola in 1530.
A brief treatment of quartz follows. For full treatment, see silica mineral.
Quartz has great economic importance. Many varieties are gemstones, including amethyst, citrine, smoky quartz, and rose quartz. Sandstone, composed mainly of quartz, is an important building stone. Large amounts of quartz sand (also known as silica sand) are used in the manufacture of glass and ceramics and for foundry molds in metal casting. Crushed quartz is used as an abrasive in sandpaper, silica sand is employed in sandblasting, and sandstone is still used whole to make whetstones, millstones, and grindstones. Silica glass (also called fused quartz) is used in optics to transmit ultraviolet light. Tubing and various vessels of fused quartz have important laboratory applications, and quartz fibres are employed in extremely sensitive weighing devices.
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Quartz is the second most abundant mineral in Earth’s crust after feldspar. It occurs in nearly all acid igneous, metamorphic, and sedimentary rocks. It is an essential mineral in such silica-rich felsic rocks as granites, granodiorites, and rhyolites. It is highly resistant to weathering and tends to concentrate in sandstones and other detrital rocks. Secondary quartz serves as a cement in sedimentary rocks of this kind, forming overgrowths on detrital grains. Microcrystalline varieties of silica known as chert, flint, agate, and jasper consist of a fine network of quartz. Metamorphism of quartz-bearing igneous and sedimentary rocks typically increases the amount of quartz and its grain size.
Quartz exists in two forms: (1) alpha-, or low, quartz, which is stable up to 573 °C (1,063 °F), and (2) beta-, or high, quartz, stable above 573 °C. The two are closely related, with only small movements of their constituent atoms during the alpha-beta transition. The structure of beta-quartz is hexagonal, with either a left- or right-handed symmetry group equally populated in crystals. The structure of alpha-quartz is trigonal, again with either a right- or left-handed symmetry group. At the transition temperature the tetrahedral framework of beta-quartz twists, resulting in the symmetry of alpha-quartz; atoms move from special space group positions to more general positions. At temperatures above 867 °C (1,593 °F), beta-quartz changes into tridymite, but the transformation is very slow because bond breaking takes place to form a more open structure. At very high pressures alpha-quartz transforms into coesite and, at still higher pressures, stishovite. Such phases have been observed in impact craters.
Quartz is piezoelectric: a crystal develops positive and negative charges on alternate prism edges when it is subjected to pressure or tension. The charges are proportional to the change in pressure. Because of its piezoelectric property, a quartz plate can be used as a pressure gauge, as in depth-sounding apparatus.
Just as compression and tension produce opposite charges, the converse effect is that alternating opposite charges will cause alternating expansion and contraction. A section cut from a quartz crystal with definite orientation and dimensions has a natural frequency of this expansion and contraction (i.e., vibration) that is very high, measured in millions of vibrations per second. Properly cut plates of quartz are used for frequency control in radios, televisions, and other electronic communications equipment and for crystal-controlled clocks and watches.
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China, Japan, and Russia are the world’s primary producers of quartz. Belgium, Brazil, Bulgaria, France, Germany, South Africa, and the United Kingdom also mine significant quantities of the mineral.
For detailed physical properties, see silica mineral (Click Here to see full-size table
table).