Quadrant Model of Reality: Quadrant Model of Reality Book 18 Silicon

PDMS – a silicone compound

Silicon forms binary compounds called silicides with many metallic elements whose properties range from reactive compounds, e.g. magnesium silicide, Mg2Si through high melting refractory compounds such as molybdenum disilicide, MoSi2.[44]

Silicon carbide, SiC (carborundum) is a hard, high melting solid and a well known abrasive. It may also be sintered into a type of high-strength ceramic used in armor.

Silane, SiH4, is a pyrophoric gas with a similar tetrahedral structure to methane, CH4. When pure, it does not react with pure water or dilute acids; however, even small amounts of alkali impurities from the laboratory glass can result in a rapid hydrolysis.[45] There is a range of catenated silicon hydrides that form a homologous series of compounds, Si

2n+2 where n = 2–8 (analogous to the alkanes). These are all readily hydrolyzed and are thermally unstable, particularly the heavier members.[46][47]

Disilenes contain a silicon-silicon double bond (analogous to the alkenes) and are generally highly reactive requiring large substituent groups to stabilize them.[48] A disilyne with a silicon-silicon triple bond was first isolated in 2004; although as the compound is non-linear, the bonding is dissimilar to that in alkynes.[49]

Tetrahalides, SiX4, are formed with all the halogens.[50] Silicon tetrachloride, for example, reacts with water, unlike its carbon analogue, carbon tetrachloride.[51] Silicon dihalides are formed by the high temperature reaction of tetrahalides and silicon; with a structure analogous to a carbene they are reactive compounds. Silicon difluoride condenses to form a polymeric compound, (SiF

n.[47]

Silicon dioxide (silica) is a high melting solid with a number of crystal forms; the most familiar of which is the mineral quartz. In crystalline quartz each silicon atom is surrounded by four oxygen atoms that bridge to other silicon atoms to form a three dimensional lattice (see below for the vitreous or glass form of pure silica). [51] Silica is soluble in water at high temperatures forming a range of compounds called monosilicic acid, Si(OH)4.[52]

Under the right conditions monosilicic acid readily polymerizes to form more complex silicic acids, ranging from the simplest condensate, disilicic acid (H6Si2O7) to linear, ribbon, layer and lattice structures which form the basis of the many silicate minerals and are called polysilicic acids {Six(OH)4–2x}n.[52]

Silica can be fused directly into glass form, as so-called fused quartz, which contains no crystalline structure. With oxides of other elements, the high temperature reaction of silicon dioxide can give a wide range of mixed glasses and glass-like network solids with various properties.[53] Examples include soda-lime glass, borosilicate glass and lead crystal glass.

Silicon sulfide, SiS2, is a polymeric solid (unlike its carbon analogue the liquid CS2).[54]

Silicon forms a nitride, Si3N4 which is a ceramic.[55] Silatranes, a group of tricyclic compounds containing five-coordinate silicon, may have physiological properties.[56]

Many transition metal complexes containing a metal-silicon bond are now known, which include complexes containing SiH

3−n ligands, SiX3 ligands, and Si(OR)3 ligands.[56]

Silicones are large group of polymeric compounds with an (Si-O-Si) backbone. An example is the silicone oil PDMS (polydimethylsiloxane). These polymers can be crosslinked to produce resins and elastomers.[57]

Many organosilicon compounds are known which contain a silicon-carbon single bond. Many of these are based on a central tetrahedral silicon atom, and some are optically active when central chirality exists. Long chain polymers containing a silicon backbone are known, such as polydimethysilylene (SiMe

n.[58] Polycarbosilane, [(SiMe

2CH

n with a backbone containing a repeating -Si-Si-C unit, is a precursor in the production of silicon carbide fibers.

Applications

Compounds

Building materials. Most silicon is used industrially without being separated into the element, and indeed often with comparatively little processing from natural occurrence. Over 90% of the Earth's crust is composed of silicate minerals, which are compounds of silicon and oxygen, often with metallic ions when negatively charged silicate anions require cations to balance the charge. Many of these have direct commercial uses, such as clays, silica sand and most kinds of building stone. Thus, the vast majority of uses for silicon are as structural compounds, either as the silicate minerals or silica (crude silicon dioxide). Silicates are used in making Portland cement (made mostly of calcium silicates) which is used in building mortar and modern stucco, but more importantly, combined with silica sand, and gravel (usually containing silicate minerals like granite), to make the concrete that is the basis of most of the very largest industrial building projects of the modern world. [59]

Ceramics and glass. Silica is used to make fire brick, a type of ceramic. Silicate minerals are also in whiteware ceramics, an important class of products usually containing various types of fired clay minerals (natural aluminium phyllosilicates). An example is porcelain which is based on the silicate mineral kaolinite. Traditional glass (silica-based soda-lime glass) also functions in many of the same ways, and is also used for windows and containers. In addition, specialty silica based glass fibers are used for optical fiber, as well as to produce fiberglass for structural support and glass wool for thermal insulation.

Artificial silicon compounds. Very occasional elemental silicon is found in nature, and also naturally-occurring compounds of silicon and carbon (silicon carbide) or nitrogen (silicon nitride) are found in stardust samples or meteorites in presolar grains, but the oxidizing conditions of the inner planets of the solar system make planetary silicon compounds found there mostly silicates and silica. Free silicon, or compounds of silicon in which the element is covalently attached to hydrogen, boron, or elements other than oxygen, are mostly artificially produced. They are described below.

Silicon compounds of more modern origin function as high-technology abrasives and new high-strength ceramics based upon silicon carbide. Silicon is a component of some superalloys.

Alternating silicon-oxygen chains with hydrogen attached to the remaining silicon bonds form the ubiquitous silicon-based polymeric materials known as silicones. These compounds containing silicon-oxygen and occasionally silicon-carbon bonds have the capability to act as bonding intermediates between glass and organic compounds, and to form polymers with useful properties such as impermeability to water, flexibility and resistance to chemical attack. Silicones are often used in waterproofing treatments, molding compounds, mold-release agents, mechanical seals, high temperature greases and waxes, and caulking compounds. Silicone is also sometimes used in breast implants, contact lenses, explosives and pyrotechnics.[60] Silly Putty was originally made by adding boric acid to silicone oil.[61]

Alloys

Elemental silicon is added to molten cast iron as ferrosilicon or silicocalcium alloys to improve performance in casting thin sections and to prevent the formation of cementite where exposed to outside air. The presence of elemental silicon in molten iron acts as a sink for oxygen, so that the steel carbon content, which must be kept within narrow limits for each type of steel, can be more closely controlled. Ferrosilicon production and use is a monitor of the steel industry, and although this form of elemental silicon is grossly impure, it accounts for 80% of the world's use of free silicon. Silicon is an important constituent of electrical steel, modifying its resistivity and ferromagnetic properties.

The properties of silicon can be used to modify alloys with metals other than iron. "Metallurgical grade" silicon is silicon of 95–99% purity. About 55% of the world consumption of metallurgical purity silicon goes for production of aluminium-silicon alloys (silumin alloys) for aluminium part casts, mainly for use in the automotive industry. Silicon's importance in aluminium casting is that a significantly high amount (12%) of silicon in aluminium forms a eutectic mixture which solidifies with very little thermal contraction. This greatly reduces tearing and cracks formed from stress as casting alloys cool to solidity. Silicon also significantly improves the hardness and thus wear-resistance of aluminium.[29][30]

Electronics

Main article: Semiconductor device fabrication

Silicon wafer with mirror finish

Most elemental silicon produced remains as ferrosilicon alloy, and only a relatively small amount (20%) of the elemental silicon produced is refined to metallurgical grade purity (a total of 1.3–1.5 million metric tons/year). The fraction of silicon metal which is further refined to semiconductor purity is estimated at only 15% of the world production of metallurgical grade silicon.[30] However, the economic importance of this small very high-purity fraction (especially the ~ 5% which is processed to monocrystalline silicon for use in integrated circuits) is disproportionately large.

Pure monocrystalline silicon is used to produce silicon wafers used in the semiconductor industry, in electronics and in some high-cost and high-efficiency photovoltaic applications. In terms of charge conduction, pure silicon is an intrinsic semiconductor which means that unlike metals it conducts electron holes and electrons that may be released from atoms within the crystal by heat, and thus increase silicon's electrical conductivity with higher temperatures. Pure silicon has too low a conductivity (i.e., too high a resistivity) to be used as a circuit element in electronics. In practice, pure silicon is doped with small concentrations of certain other elements, a process that greatly increases its conductivity and adjusts its electrical response by controlling the number and charge (positive or negative) of activated carriers. Such control is necessary for transistors, solar cells, semiconductor detectors and other semiconductor devices, which are used in the computer industry and other technical applications. For example, in silicon photonics, silicon can be used as a continuous wave Raman laser medium to produce coherent light, though it is ineffective as an everyday light source.

In common integrated circuits, a wafer of monocrystalline silicon serves as a mechanical support for the circuits, which are created by doping, and insulated from each other by thin layers of silicon oxide, an insulator that is easily produced by exposing the element to oxygen under the proper conditions. Silicon has become the most popular material to build both high power semiconductors and integrated circuits. The reason is that silicon is the semiconductor that can withstand the highest temperatures and electrical powers without becoming dysfunctional due to avalanche breakdown (a process in which an electron avalanche is created by a chain reaction process whereby heat produces free electrons and holes, which in turn produce more current which produces more heat). In addition, the insulating oxide of silicon is not soluble in water, which gives it an advantage over germanium (an element with similar properties which can also be used in semiconductor devices) in certain type of fabrication techniques.[62]

Monocrystalline silicon is expensive to produce, and is usually only justified in production of integrated circuits, where tiny crystal imperfections can interfere with tiny circuit paths. For other uses, other types of pure silicon which do not exist as single crystals may be employed. These include hydrogenated amorphous silicon and upgraded metallurgical-grade silicon (UMG-Si) which are used in the production of low-cost, large-area electronics in applications such as liquid crystal displays, and of large-area, low-cost, thin-film solar cells. Such semiconductor grades of silicon which are either slightly less pure than those used in integrated circuits, or which are produced in polycrystalline rather than monocrystalline form, make up roughly similar amount of silicon as are produced for the monocrystalline silicon semiconductor industry, or 75,000 to 150,000 metric tons per year. However, production of such materials is growing more quickly than silicon for the integrated circuit market. By 2013 polycrystalline silicon production, used mostly in solar cells, is projected to reach 200,000 metric tons per year, while monocrystalline semiconductor silicon production (used in computer microchips) remains below 50,000 tons/year.[30]

Mechanical watches

Since 2000, silicon has found a new use in mechanical watch movements. Several manufacturers of mechanical watch movements have incorporated silicon parts, mainly in the escapements and balance wheel regions. Silicon hair-springs are becoming more common as are silicon escapement wheels and forks. Silicon has several desirable properties when used in these contexts; It is thermally stable, shock resistant, and requires little to no lubrication. Ulysse Nardin pioneered these applications, with Omega, Breguet, Patek, Rolex, Cartier, and Damasco following.[63] Most of these parts for watch movements are manufactured using deep reactive-ion etching (DRIE).[64]

Biological role

Silica skeletons of radiolaria in false color.

Although silicon is readily available in the form of silicates, very few organisms have a use for it. Diatoms, radiolaria and siliceous sponges use biogenic silica as a structural material to construct skeletons. In more advanced plants, the silica phytoliths (opal phytoliths) are rigid microscopic bodies occurring in the cell; some plants, for example rice, need silicon for their growth.[65][66][67] The possible biological potential of silicon as bioavailable orthosilicic acid and the potential beneficial effects on human health has been reviewed.[68]

Silicon is needed for synthesis of elastin and collagen;[not in citation given] the aorta contains the highest quantity of elastin and silicon.[69] Silicon is currently under consideration for elevation to the status of a "plant beneficial substance by the Association of American Plant Food Control Officials (AAPFCO)."[70][71] Silicon has been shown in university and field studies to improve plant cell wall strength and structural integrity,[72] improve drought and frost resistance, decrease lodging potential and boost the plant's natural pest and disease fighting systems.[73] Silicon has also been shown to improve plant vigor and physiology by improving root mass and density, and increasing above ground plant biomass and crop yields.[72]

printed silicon electronics wiki

QMRSilicon Valley is a nickname for the southern portion of the San Francisco Bay Area, which is located in part of the U.S. state of California known as Northern California. It is home to many of the world's largest high-tech corporations, as well as thousands of startup companies. Geographically, it encompasses all of the Santa Clara Valley, the southern half of the San Francisco Peninsula, and southern portions of the East Bay. It includes parts or most of Santa Clara County, San Mateo County, and Alameda County.

The word "valley" refers to the Santa Clara Valley, where the region has traditionally been centered, which includes the city of San Jose and surrounding cities and towns. The word "silicon" originally referred to the large number of silicon chip innovators and manufacturers in the region. The term "Silicon Valley" eventually came to refer to all high tech businesses in the area, and is now generally used as a synecdoche for the American high-technology economic sector. It also became a global synonym for leading high-tech research and enterprises, and thus inspired similar named locations, as well as research parks and technology centers with a comparable structure all around the world.

Silicon Valley is a leading hub and startup ecosystem for high-tech innovation and development, accounting for one-third of all of the venture capital investment in the United States. It was in the Valley that the silicon-based integrated circuit, the microprocessor, and the microcomputer, among other key technologies, were developed. As of 2013, the region employed about a quarter of a million information technology workers.[1]

QMRBlack silicon is a semiconductor material, a surface modification of silicon with very low reflectivity and correspondingly high absorption of visible (and infrared) light. The modification was discovered in the 1980s as an unwanted side effect of reactive ion etching (RIE).[1][2] Other methods for forming a similar structure include electrochemical etching, stain etching, metal-assisted chemical etching, and laser treatment (which is developed in Eric Mazur's laboratory at Harvard University ), and FFC Cambridge process (an electrochemical reduction process).

Properties[edit]

Scanning electron micrograph of black silicon, produced by RIE (ASE process)

SEM micrograph of black silicon formed by cryogenic RIE. Notice the smooth, sloped surfaces, unlike the undulated sidewalls obtained with the Bosch process RIE.

Black silicon is a needle-shaped surface structure where needles are made of single-crystal silicon and have a height above 10 µm and diameter less than 1 µm.[2] Its main feature is an increased absorption of incident light—the high reflectivity of the silicon, which is usually 20–30% for quasi-normal incidence, is reduced to about 5%. This is due to the formation of a so-called effective medium[4] by the needles. Within this medium, there is no sharp interface, but a continuous change of the refractive index that reduces Fresnel reflection. When the depth of the graded layer is roughly equal to the wavelength of light in silicon (about one-quarter the wavelength in vacuum) the reflection is reduced to 5%; deeper grades produce even blacker silicon.[5] For low reflectivity, the nanoscale features producing the index graded layer must be smaller than the wavelength of the incident light to avoid scattering.[5]

Applications[edit]

The unusual optical characteristics, combined with the semiconducting properties of silicon make this material interesting for sensor applications. Potential applications include:[6]

Image sensors with increased sensitivity

Thermal imaging cameras

Photodetector with high-efficiency through increased absorption.[7][8]

Mechanical contacts and interfaces [2]

Terahertz applications.[9][10][11][12]

Solar cells[3][13][14]

Antibacterial surfaces[15] that work by physically rupturing bacteria's cellular membranes.

Production[edit]

Reactive-ion etching[edit]

Scanning electron micrograph of a single "needle" of black silicon, produced by RIE (ASE process)

In semiconductor technology, reactive-ion etching (RIE) is a standard procedure for producing trenches and holes with a depth of up to several hundred micrometres and very high aspect ratios. In Bosch process RIE, this is achieved by repeatedly switching between an etching and passivation. With cryogenic RIE, the low temperature and oxygen gas achieve this sidewall passivation by forming SiO

2, easily removed from the bottom by directional ions. Both RIE methods can produce black silicon, but the morphology of the resulting structure differs substantially. The switching between etching and passivation of the Bosch process creates undulated sidewalls, which are visible also on the black silicon formed this way.

During etching, however, small debris remain on the substrate; they mask the ion beam and produce structures that are not removed and in the following etching steps and result in tall silicon pillars.[16] The process can be set so that a million needles are formed on an area of one square millimeter.[12]

Mazur's method[edit]

In 1999, a Harvard University group developed a process in which black silicon was produced by irradiating silicon with femtosecond laser pulses.[17] After irradiation in the presence of a gas containing sulfur hexafluoride and other dopants, the surface of silicon develops a self-organized microscopic structure of micrometer-sized cones. The resulting material has many remarkable properties, such as absorption that extends to the infrared range, below the band gap of silicon, including wavelengths for which ordinary silicon is transparent. sulfur atoms are forced to the silicon surface, creating a structure with a lower band gap and therefore the ability to absorb longer wavelengths.

Black silicon made without special gas ambient - laboratory LP3-CNRS

Similar surface modification can be achieved in vacuum using the same type of laser and laser processing conditions. In this case, the individual silicon cones lack sharp tips (see image). The reflectivity of such a micro-structured surface is very low, 3-14% in the spectral range 350–1150 nm.[18] Such reduction in reflectivity is contributed by the cone geometry, which increases the light internal reflections between them. Hence, the possibility of light absorption is increased. The gain in absorption achieved by fs laser texturization was superior to that achieved by using an alkaline chemical etch method,[19] which is a standard industrial approach for surface texturing of mono-crystalline silicon wafers in solar cell manufacturing. Such surface modification is independent of local crystalline orientation. A uniform texturing effect can be achieved across the surface of a multi-crystalline silicon wafer. The very steep angles lower the reflection to near zero and also increase the probability of recombination, keeping it from use in solar cells

Production[edit]

Reactive-ion etching[edit]

Scanning electron micrograph of a single "needle" of black silicon, produced by RIE (ASE process)

Mazur's method[edit]

Black silicon made without special gas ambient - laboratory LP3-CNRS

Nanopores[edit]

When a mix of copper nitrate, phosphorous acid, hydrogen fluoride and water are applied to a silicon wafer, the phosphorous acid reduction reduces the copper ions to copper nanoparticles. The nanoparticles attract electrons from the wafer’s surface, oxidizing it and allowing the hydrogen fluoride to burn inverted pyramid-shaped nanopores into the silicon. The process produced pores as small as 590 nm that let through more than 99% of light.[20]

Function[edit]

When the material is biased by a small electric voltage, absorbed photons are able to excite dozens of electrons. The sensitivity of black silicon detectors is 100–500 times higher than that of untreated silicon (conventional silicon), in both the visible and infrared spectra.[21][22]

A group at the National Renewable Energy Laboratory reported black silicon solar cells with 18.2% efficiency.[14] This black silicon anti-reflective surface was formed by a metal-assisted etch process using nano particles of silver. In May 2015, researchers from Finland's Aalto University, working with researchers from Universitat Politècnica de Catalunya announced they had created black silicon solar cells with 22.1% efficiency[23][24] by applying a thin passivating film on the nanostructures by Atomic Layer Deposition, and by integrating all metal contacts on the back side of the cell.

A team led by Elena Ivanova at Swinburne University of Technology in Melbourne discovered in 2012[25] that cicada wings were potent killers of Pseudomonas aeruginosa, an opportunist germ that also infects humans and is becoming resistant to antibiotics. The effect came from regularly-spaced "nanopillars" on which bacteria were sliced to shreds as they settled on the surface.

Both cicada wings and black silicon were put through their paces in a lab, and both were bactericidal. Smooth to human touch, the surfaces destroyed Gram-negative and Gram-positive bacteria, as well as bacterial spores.

The three targeted bacterial species P. aeruginosa, Staphylococcus aureus and Bacillus subtilis, a wide-ranging soil germ that is a cousin of anthrax.

The killing rate was 450,000 bacteria per square centimetre per minute over the first three hours of exposure or 810 times the minimum dose needed to infect a person with S. aureus, and 77,400 times that of P. aeruginosa.

QMRSilicon tombac

From Wikipedia, the free encyclopedia

Silicon tombac (German word origin: Siliziumtombak) is an alloy made of copper (80%), zinc (16%) and silicon (4%).

Silicon tombac

From Wikipedia, the free encyclopedia

Silicon tombac (German word origin: Siliziumtombak) is an alloy made of copper (80%), zinc (16%) and silicon (4%).

General properties[edit]

The silicon content leads to a strengthening of the metal matrix. The appearance is similar to ordinary brass. Silicon tombac has good friction bearing characteristics and is corrosion resistant but is not resistant to ammonia atmosphere. The strength properties are largely retained at application temperatures up to 200 °C.[1] It is a special alloy in terms of the combination of casting process and casting temperature. In most cases, parts made of silicon tombac, are produced through the high pressure die casting process, which is normally specialized on metals with relatively low melting temperatures. But in this case the temperature melting range of silicon tombac is in the area of 950 to 1000 °C, which is relatively high for casting into permanent moulds. The advantage is the productivity of this highly automated casting process. The disadvantage is the temperature stress of the surface of the permanent mould, so that the lifetime of these moulds is limited.

Comparison to investment cast steel parts[edit]

High pressure die cast Silicon tombac is often used as an alternative for investment cast steel parts, because the mechanical strength is comparable (500 MPa [1]), but the production process is more efficient. There can be found a break-even-point when comparing both processes, whereas the advantages of high pressure die casting regularly predominate at high unit numbers (for instance greater than 5000 units [2]) to produce. This alloy has outstanding casting properties and good strength properties,[3] which is required for the die casting process. It is often chosen for small to medium size parts in terms of casting metal volume. For large parts often investment casting of steels is applied because of the lower material cost.

Metallurgical aspects[edit]

The silicon content limits the solubility of zinc in copper in the α-phase. In the given alloy the maximum amount of silicon at a very high zinc content is added. The consequence is that the α-phase crystallized silicon supersaturated when it comes to high cooling rates of the alloy. As a result the α-solid solution does not disintegrate, which leads to the described high mechanical properties.

QMRBiasing resistor[edit]

R1 acts as a feedback resistor, biasing the inverter in its linear region of operation and effectively causing it to function as a high gain inverting amplifier. To see this, assume the inverter is ideal, with infinite input impedance and zero output impedance. The resistor forces the input and output voltages to be equal. Hence the inverter will neither be fully on nor fully off, but will operate in the transition region where it has gain.

Resonator[edit]

Extremely low cost applications sometimes use a piezoelectric PZT crystal ceramic resonator rather than a piezoelectric quartz crystal resonator.

The crystal in combination with C1 and C2 forms a pi network band-pass filter, which provides a 180 degree phase shift and a voltage gain from the output to input at approximately the resonant frequency of the crystal. To understand the operation, note that at the frequency of oscillation, the crystal appears inductive. Thus, the crystal can be considered a large, high Q inductor. The combination of the 180 degree phase shift (i.e. inverting gain) from the pi network, and the negative gain from the inverter, results in a positive loop gain (positive feedback), making the bias point set by R1 unstable and leading to oscillation.

QMRQuartz is the second-most-abundant mineral in Earth's continental crust, after feldspar. Its crystal structure is a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical formula of SiO2.

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 Europe and the Middle East.

Recall that silicon has four valence electrons. It is known as the miracle element and is shaped as a quadrant. Quartz is tetrahedral in shape. Tetra means four.

Modern watches use quartz as a time keeping device.

The word "quartz" is derived from the German word "Quarz" and its Middle High German ancestor "twarc", which probably originated in Slavic, cf. Czech tvrdý ("hard"), Polish twardy ("hard"), Serbian and Croatian tvrd ("hard").[7]

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.[8] Today, the term rock crystal is sometimes used as an alternative name for the purest form of quartz.

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, 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 and P3221 respectively. β-quartz belongs to the hexagonal system, space group P6222 and P6422, respectively.[9] 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 are linked.

Varieties (according to color)

Clear rock crystals on a white base

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.[10] 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

Amethyst crystals on matrix

Amethyst is a popular 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.

Citrine

Citrine from Brazil

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 tell cut citrine from 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 Latin 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.[11] Citrine has been referred to as the "merchant's stone" or "money stone", due to a superstition that it would bring prosperity.[12]

Rose quartz

Rose quartz cluster (Size: 3.4 x 3.1 x 1.9 cm)

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 massive 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 massive quartz.[13]

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.[14]

Smoky quartz from the Alps

Smoky quartz

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.

Milky quartz

Milky quartz sample

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,[citation needed] making it of little value for optical and quality gemstone applications.[15]

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

Chalcedony Cryptocrystalline quartz and moganite mixture. The term is 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 cryptocrystalline quartz, typically red to brown

Aventurine Translucent chalcedony with small inclusions (usually mica) that shimmer.

Tiger's eye Fibrous gold to red-brown colored quartz, exhibiting chatoyancy.

Rock crystal Clear, colorless

Amethyst Purple, transparent

Citrine Yellow to reddish orange to brown, greenish yellow

Prasiolite Mint green, transparent

Rose quartz Pink, translucent, may display diasterism

Rutilated quartz Contains acicular (needle-like) inclusions of rutile

Milky quartz White, translucent to opaque, may display diasterism

Smoky quartz Brown to gray, opaque

Carnelian Reddish orange chalcedony, translucent

Dumortierite quartz Contains large amounts of dumortierite crystals

Major varieties of quartz

Chalcedony Cryptocrystalline quartz and moganite mixture. The term is 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 cryptocrystalline quartz, typically red to brown

Aventurine Translucent chalcedony with small inclusions (usually mica) that shimmer.

Tiger's eye Fibrous gold to red-brown colored quartz, exhibiting chatoyancy.

Rock crystal Clear, colorless

Amethyst Purple, transparent

Citrine Yellow to reddish orange to brown, greenish yellow

Prasiolite Mint green, transparent

Rose quartz Pink, translucent, may display diasterism

Rutilated quartz Contains acicular (needle-like) inclusions of rutile

Milky quartz White, translucent to opaque, may display diasterism

Smoky quartz Brown to gray, opaque

Carnelian Reddish orange chalcedony, translucent

Dumortierite quartz Contains large amounts of dumortierite crystals

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.[16] 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 heat-treated amethyst. Carnelian is widely heat-treated to deepen its color.

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.

Occurrence

Quartz is a defining constituent of granite and other felsic igneous rocks. It is very common in sedimentary rocks such as sandstone and shale and is also present in variable amounts as an accessory mineral in most carbonate rocks. 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 and consequently it is very common as a residual mineral in stream sediments and residual soils.

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 kilograms.

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.[17]

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.[18]

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.

History

Fatimid ewer in carved rock crystal (clear quartz) with gold lid, c. 1000

Quartz crystal demonstrating transparency

The word "quartz" comes from the German About this sound Quarz (help·info),[19] 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.[20]

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, such as Newgrange or Carrowmore in Ireland. The Irish word for quartz is grian cloch, which means 'stone of the sun'. 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.[21]

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.

Roman naturalist Pliny the Elder believed quartz to be water ice, permanently frozen after great lengths of time.[22] (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.[23]

Quartz's piezoelectric properties were discovered by Jacques and Pierre Curie in 1880.[24][25] The quartz oscillator or resonator was first developed by Walter Guyton Cady in 1921.[26][27] George Washington Pierce designed and patented quartz crystal oscillators in 1923.[28][29][30] Warren Marrison created the first quartz oscillator clock based on the work of Cady and Pierce in 1927.[31]

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: German geologist Karl Emil von Schafhäutl (1803–1890)[32] was the first person to synthesize quartz when in 1845 he created microscopic quartz crystals in a pressure cooker.[33] However, the quality and size of the crystals that were produced by these early efforts were poor.[34] 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.[35] 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.[36][37] (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.[38][39] 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 electronic industry is synthetic.

Piezoelectricity

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 monitors.

QMRA quartz clock is a clock that uses an electronic oscillator that is regulated by a quartz crystal to keep time. This crystal oscillator creates a signal with very precise frequency, so that quartz clocks are at least an order of magnitude more accurate than mechanical clocks. Generally, some form of digital logic counts the cycles of this signal and provides a numeric time display, usually in units of hours, minutes, and seconds. The first quartz clock was built in 1927 by Warren Marrison and J.W. Horton at Bell Telephone Laboratories. Since the 1980s when the advent of solid state digital electronics allowed them to be made compact and inexpensive, quartz timekeepers have become the world's most widely used timekeeping technology, used in most clocks and watches, as well as computers and other appliances that keep time.

Explanation[edit]

First European quartz clock for consumers "Astrochron", Junghans, Schramberg, 1967 (German Clock Museum, Inv. 1995-603)

First quartz wristwatch movement Caliber 35A, Nr. 00234, Seiko, Japan, 1969 (German Clock Museum, Inv. 2010-006)

Chemically, quartz is a compound called silicon dioxide. Many materials can be formed into plates that will resonate. However, quartz is also a piezoelectric material: that is, when a quartz crystal is subject to mechanical stress, such as bending, it accumulates electrical charge across some planes. In a reverse effect, if charges are placed across the crystal plane, quartz crystals will bend. Since quartz can be directly driven (to flex) by an electric signal, no additional speaker or microphone is required to use it in a resonator. Similar crystals are used in low-end phonograph cartridges: The movement of the stylus (needle) flexes a quartz crystal, which produces a small voltage, which is amplified and played through speakers. Quartz microphones are still available, though not common.

Quartz has a further advantage in that its size does not change much as temperature fluctuates. Fused quartz is often used for laboratory equipment that must not change shape along with the temperature. A quartz plate's resonance frequency, based on its size, will not significantly rise or fall. Similarly, since its resonator does not change shape, a quartz clock will remain relatively accurate as the temperature changes.

In the early 20th century, radio engineers sought a precise, stable source of radio frequencies, and started at first with steel resonators. However, when Walter Guyton Cady found that quartz can resonate with less equipment and better temperature stability, steel resonators disappeared within a few years. Later, scientists at NIST (Then the U.S. National Bureau of Standards) discovered that a crystal oscillator could be more accurate than a pendulum clock.

The electronic circuit is an oscillator, an amplifier whose output passes through the quartz resonator. The resonator acts as an electronic filter, eliminating all but the single frequency of interest. The output of the resonator feeds back to the input of the amplifier, and the resonator assures that the oscillator "howls" with the exact frequency of interest. When the circuit starts up, even a single shot can cascade to bringing the oscillator at the desired frequency. If the amplifier is too perfect, the oscillator will not start.

The frequency at which the crystal oscillates depends on its shape, size, and the crystal plane on which the quartz is cut. The positions at which electrodes are placed can slightly change the tuning, as well. If the crystal is accurately shaped and positioned, it will oscillate at a desired frequency. In nearly all quartz watches, the frequency is 32,768 Hz,[1] and the crystal is cut in a small tuning fork shape on a particular crystal plane. This frequency is a power of two (32,768 = 215), just high enough so most people cannot hear it, yet low enough to permit inexpensive counters to derive a 1-second pulse. A 15-bit binary digital counter driven by the frequency will overflow once per second, creating a digital pulse once per second. The pulse-per-second output can be used to drive many kinds of clocks.

Although quartz has a very low coefficient of thermal expansion, temperature changes are the major cause of frequency variation in crystal oscillators. The most obvious way of reducing the effect of temperature on oscillation rate is to keep the crystal at a constant temperature. For laboratory grade oscillators an Oven-Controlled Crystal Oscillator is used, in which the crystal is kept in a very small oven that is held at a constant temperature. This method is however impractical for consumer quartz clock and wrist watch movements.

The crystal planes and tuning of a consumer grade clock crystal are designed for minimal temperature sensitivity in terms of their effect on frequency and operate best at about 25 to 28 °C (77 to 82 °F). At that temperature the crystal oscillates at its fastest. A higher or lower temperature will result in a -0.035 parts per million/°C2 (slower) oscillation rate. So a ±1 °C temperature deviation will account for a (1)2 x -0.035 = -0.035 parts per million (ppm) rate, which is equivalent to -1.1 seconds per year. If, instead, the crystal experiences a ±10 °C temperature deviation, then the rate change will be (10)2 x -0.035 ppm = 100 x -0.035 ppm = -3.5 ppm, which is equivalent to -110 seconds per year.

Quartz watch manufacturers use a simplified version of the Oven-Controlled Crystal Oscillator method by recommending that their watches be worn regularly to ensure best performance. Regular wearing of a quartz watch significantly reduces the magnitude of environmental temperature swings, since a correctly designed watch case forms an expedient crystal oven that uses the stable temperature of the human body to keep the crystal in its most accurate temperature range.

Mechanism[edit]

Basic quartz wristwatch movement. Bottom right quartz crystal oscillator, left button cell watch battery. Top right oscillator counter, top left the coil of the stepper motor that powers the watch hands.

Picture of a quartz crystal resonator, used as the timekeeping component in quartz watches and clocks, with the case removed. It is formed in the shape of a tuning fork. Most such quartz clock crystals vibrate at a frequency of 32,768 Hz.

In modern quartz clocks, the quartz crystal resonator or oscillator is in the shape of a small tuning fork, laser-trimmed or precision lapped to vibrate at 32,768 Hz. This frequency is equal to 215 cycles per second. A power of 2 is chosen so a simple chain of digital divide-by-2 stages can derive the 1 Hz signal needed to drive the watch's second hand. In most clocks, the resonator is in a small can or flat package, about 4 mm long. The reason the 32,768 Hz resonator has become so common is due to a compromise between the large physical size of low frequency crystals for watches and the large current drain of high frequency crystals, which reduces the life of the watch battery. During the 1970s, the introduction of metal–oxide–semiconductor (MOS) integrated circuits allowed a 12-month battery life from a single coin cell when driving either a mechanical Lavet type stepping motor or a liquid crystal display (in an LCD digital watch). Light-emitting diode (LED) displays for watches have become rare due to their comparatively high battery consumption.

The basic formula for calculating the fundamental frequency (f) of vibration of a cantilever as a function of its dimensions (quadratic cross-section) is:[2]

f = \frac{1.875^2}{2\pi} \frac{a}{l^2} \sqrt \frac{E}{12 \rho}

where

1.875 the smallest positive solution of cos(x)cosh(x) = -1 [3]

l is the length of the cantilever

a is its thickness along the direction of motion

E is its Young's modulus

and ρ is its density

A cantilever made of quartz (E = 1011 N·m−2 = 100 GPa and ρ = 2634 kg·m−3 [4]) with a length of 3 mm and a thickness of 0.3 mm has thus a fundamental frequency of around 33 kHz. The crystal is tuned to exactly 215 = 32,768 Hz or runs at a slightly higher frequency with inhibition compensation (see below).

Accuracy[edit]

The relative stability of the resonator and its driving circuit is much better than its absolute accuracy. Standard-quality resonators of this type are warranted to have a long-term accuracy of about 6 parts per million (0.0006%) at 31 °C (87.8 °F): that is, a typical quartz clock or wristwatch will gain or lose 15 seconds per 30 days (within a normal temperature range of 5 °C/41 °F to 35 °C/95 °F) or less than a half second clock drift per day when worn near the body.

Inhibition compensation[edit]

Many inexpensive quartz clocks and watches use a technique known as inhibition compensation.[1] The crystal is deliberately made to run somewhat fast, and after manufacture each module is adjusted to keep accurate time by programming the digital logic to skip a small number of crystal cycles at regular intervals such as 10 seconds or 1 minute. For a typical quartz movement this allows programmed adjustments in 7.91 seconds per 30 days increments for 10 second intervals (on a 10-second measurement gate) or programmed adjustments in 1.32 seconds per 30 days increments for 60 seconds intervals (on a 60-second measurement gate). The advantage of this method is that after measuring the frequency of each chip with a precision timer at the factory, storing the number of pulses to suppress in a non-volatile memory register on the chip is less expensive than the older technique of trimming the quartz tuning fork frequency. The inhibition compensation logic of some quartz movements can be regulated by service centers with the help of a precision timer and adjustment terminal after leaving the factory, though many inexpensive quartz watch movements do not offer this functionality.

Internal adjustment[edit]

Some premium movement designs self-rate and self-regulate. That is, rather than just counting vibrations, their computer program takes the simple count, and scales it using a ratio calculated between an epoch set at the factory, and the most recent time the clock was set. These clocks usually have special instructions for changing the battery (the counter must not be permitted to stop), and become more accurate as they age.[citation needed]

It is possible for a computerized high accuracy quartz movement to measure its temperature, and adjust for that as well. Both analog and digital temperature compensation have been used in high-end quartz watches. In more expensive high end quartz watches, thermal compensation can be implemented by varying the number of cycles to inhibit depending on the output from a temperature sensor. The COSC average daily rate standard for officially certified COSC quartz chronometers is ± 25.55 seconds per year. Thermo compensated quartz movements, even in wrist watches, can be accurate to within ± 5 to ± 25 seconds per year and can be used as marine chronometers to determine longitude by means of celestial navigation.[5][6][7]

External adjustment[edit]

If a quartz movement is "rated" by measuring its timekeeping characteristics against a radio clock's time broadcast, to determine how much time the watch gains or loses per day, and adjustments are made to the circuitry to "regulate" the timekeeping, then the corrected time will easily be accurate within ± 10 seconds per year. This is more than adequate to perform celestial navigation.

Chronometers[edit]

Quartz chronometers designed as time standards often include a crystal oven, to keep the crystal at a constant temperature. Some self-rate and include "crystal farms," so that the clock can take the average of a set of time measurements.

History[edit]

Four precision 100 kHz quartz oscillators at the US Bureau of Standards (now NIST) that became the first quartz frequency standard for the United States in 1929. Kept in temperature-controlled ovens to prevent frequency drift due to thermal expansion or contraction of the large quartz resonators (mounted under the glass domes on top of the units) they achieved accuracy of 10−7, roughly 1 second error in 4 months.

The first Swiss quartz clock, which was made after WW II (left), on display at the International Watchmaking Museum in La Chaux-de-Fonds.

The piezoelectric properties of quartz were discovered by Jacques and Pierre Curie in 1880. The first quartz crystal oscillator was built by Walter G. Cady in 1921. In 1923, D. W. Dye at the National Physical Laboratory in the UK and Warren Marrison at Bell Telephone Laboratories produced sequences of precision time signals with quartz oscillators. In 1927, the first quartz clock was built by Warren Marrison and J.W. Horton at Bell Telephone Laboratories.[8][9] The next 3 decades saw the development of quartz clocks as precision time standards in laboratory settings; the bulky delicate counting electronics, built with vacuum tubes, limited their use elsewhere. In 1932 a quartz clock was able to measure tiny variations in the rotation rate of the Earth over periods as short as a few weeks.[10] In Japan in 1932, Issac Koga developed a crystal cut that gave an oscillation frequency independent of temperature variation.[11][12][13] The National Bureau of Standards (now NIST) based the time standard of the US on quartz clocks between the 1930s and the 1960s, then it went to atomic clocks, but actually, in 2014, they used a quartz clock that was so accurate, they simply use an atomic clock to update it every 24 hours.[14] The wider use of quartz clock technology had to await the development of cheap semiconductor digital logic in the 1960s. The revised 14th edition of Encyclopedia Britannica[when?] stated that quartz clocks would probably never be affordable enough to be used domestically.

The world's first prototype analog quartz wristwatches were revealed in 1967: the Beta 1 revealed by the Centre Electronique Horloger (CEH) in Neuchâtel Switzerland,[15][16] and the prototype of the Astron revealed by Seiko in Japan. (Seiko had been working on quartz clocks since 1958).[15]

In 1969, Seiko produced the world's first commercial quartz wristwatch, the Astron.,[17] this watch was released just prior to the introduction of the Swiss Beta21, which was developed by 16 Swiss Watch manufactures and used by Rolex, Patek and famously Omega in their electroquartz models. The Beta 21 watches had an accuracy of 5 seconds per month but were swiftly overtaken by the introduction of more economical and accurate quartz watches. The inherent accuracy and low cost of production has resulted in the proliferation of quartz clocks and watches since that time. By the 1980s, quartz technology had taken over applications such as kitchen timers, alarm clocks, bank vault time locks, and time fuzes on munitions, from earlier mechanical balance wheel movements, an upheaval known in watchmaking as the quartz crisis.

Quartz timepieces have dominated the wristwatch and clock market since the 1980s, Because of the high Q factor and low temperature coefficient of the quartz crystal they are more accurate than the best mechanical timepieces, and the elimination of all moving parts makes them more rugged and eliminates the need for periodic maintenance.

Commercial analog and digital wall clocks became available in 2014 that utilize a double oven quartz oscillator, accurate to 0.2 ppb. These clocks are factory synchronized with the atomic time standard and typically do not require any further time adjustments for the life of the clock.

Automatic quartz is a collective term describing watch movements that combine a self-winding rotor mechanism (as used in automatic mechanical watches) to generate electricity with a piezoelectric quartz crystal as its timing element. Such movements aim to provide the advantages of quartz without the environmental impact of batteries. Several manufacturers employ this technique.

Applications[edit]

Seiko[edit]

Japanese company Seiko pioneered the technique which it unveiled at the Baselworld 1986 trade show under the trial name AGM.[1] The first such watch was released in Germany in January 1988 and April of the same year in Japan (under the name Auto-Quartz).[2] The watches had an average monthly rate of ±15 sec and provided 75 hours of continuous operation when fully powered. Early automatic quartz movements were called AGS (Automatic Generating System); in 1991 the company introduced the Kinetic brand name. Today Seiko offers a wide range of watches with various Kinetic movements. The top of the line is the caliber 9T82, included in Sportura (international brand) and PROSPEX (only marketed in Japan) Collection. It is sold in limited volume at a price range of about US$3000 which makes it one of the most expensive automatic quartz watches. Kinetic technology has also been used in some of Seiko's Pulsar and Lorus watches. As of 2007, Seiko has sold more than eight million automatic quartz watches.[1]

The different calibres of Kinetic watches currently are relatively large and heavy, weighing in at 1/3 of a pound (150 grams) or more on many models. Therefore, most Seiko Kinetic watches are only available in a men's size.

Movement calibers：

1M20

3M21 3M22

3M62

4M21

4M71

5D22* 5D44* (Direct Drive)

5D88 (Direct Drive Moonphase)

5J21* 5J22* (Auto Relay)

5J32* (Auto Relay)

5M22 5M23 5M25

5M42 5M43 5M45 5M47

5M54* (Retrograde Day Indicator)

5M62* 5M63* 5M65(GMT)*

5M82 5M83 5M84

7D46* 7D48* 7D56* (Auto Relay, Perpetual Calendar)

7L22* (Flyback chronograph)

7M12 7M42

7M22 7M45

9T82* (Chronograph)

YT57* YT58

(*) In use as of at Aug-2008

ETA[edit]

Omega Seamaster 200 Omegamatic. This watch uses Omega caliber 1400 (ETA 205.111 Rhodium plated).

Swatch Swiss Autoquarz, 1998

Swiss company ETA SA, part of the Swatch group, made seven different automatic quartz movements, calling them Autoquartz. They were part of the premium Flatline series of movements and were sold to a variety of watch vendors, primarily European and American. High grade movements designed to last as long as their premium mechanical movements, they had between 15 to 53 jewels. Unlike most quartz watches, Autoquartz could be calibrated to increase their accuracy. Several vendors had their Autoquartz watches COSC certified. In 2006 to increase production of its highly demanded mechanical movements, Swatch discontinued supplying the Autoquartz line to customers (service and parts are still available). Then in 2009, possibly due to available production capacity or stocked parts, Tissot reintroduced the Autoquartz in its PRC200 dive watch. The Autoquartz movement used by Tissot is gold plated and carries the designation ETA 205.914.

Movement calibers:

204.901 (small 8.75 lignes used primarily in women's watches)

204.911 (replacement for the 204.901 upgrading from a capacitor to a rechargeable battery)

205.111 (discontinued and replaced by the 205.911 which upgraded from a capacitor to a rechargeable battery)

205.711 (15 jeweled movement used only by Swatch Watch for a variety of its fashion watches)

205.911 (the most commonly available movement having 17 jewels and often ordered in gold plating)

205.914 (no information available from ETA)

205.961 (a 205.911 with the addition of a GMT hand)

206.211 (a 205.911 fitted with a Dubois Depraz 2021 to make a chronograph. With 53 jewels the most jeweled quartz movement ever made)

Manufacturers who employ or employed ETA movements: Tissot, Rado in their Accustar line of watches, Longines, Swatch, Omega (Omega Seamaster Omega-matic), Dugena (K-Tech), Wenger (GST Field Terragraph Autoquartz), Hermès (Nomade), Roberge (Altaïr), Mido (Multifort), Bovet (Autoquartz calibre 11BQ01), Fortis (Spacematic Eco), Belair (Autoquartz), Franck Muller (Transamerica), HTO (Grand Voyager) and Cyma.

Citizen[edit]

Citizen, one of the world's largest watch manufacturers, also built an autoquartz-powered watch: the Eco-Drive Duo (released in December 1998).[3] Novel to this watch was the use of both mechanical power as well as a solar cell. This model was an attempt to enter higher-priced markets (at a cost of around $1000 USD), but the technology failed to attract consumer interest and Citizen has since stopped making use of the unique movement. No other autoquartz powered watch from Citizen is known; all other Eco-Drive models only use solar power or thermal power.

Ventura[edit]

Ventura is a small Swiss watch manufacturer claiming to be "the World's only manufacturer of automatic digital watches". Their VEN_99 movement was the only watch to ever combine autoquartz and digital readout of time (LCD) in one package. Offered were three models: the Sparc rx, fx and px. In late 2006, the company started selling their movement with an incorporated alarm, another exclusive feature. All hardware is proprietary to Ventura.

In 2007 the company went into bankruptcy.[4] Support was available from an independent entity. In 2011 the company re-emerged from bankruptcy and continued to sell its models, introducing the "2nd gen Micro-Generating-System" and marketing the watch (Sparc MGS) integrating it as the world's first and only digital-readout multi-function automatic quartz module.[5] Unlike with other manufacturers the watch movement (VEN_10) and power source (MGS) are separate units, only linked by a single wire.

Pricing[edit]

In spite of the relatively complex mechanical parts used, Seiko has positioned their kinetic watches to be medium-priced. Exceptions are kinetic with other complications such as chronograph movement 9T82, 7L22 and direct drive movements. ETA sold Autoquartz to a variety of Swiss manufacturers with pricing below $100 (Swatch) to multiple thousands (Omega, Baume et Mercier, et al.).[citation needed] Ventura prices its automatic quartz watches at around 2000-4000 Euro.[citation needed]

QMRAutomatic quartz or kinetic movement[edit]

After the introduction of quartz watches, electronic automatic quartz watches powered by arm movement were developed by Seiko. Typically a weighted rotor turns a tiny electrical generator, charging a rechargeable battery or low-leakage capacitor, which powers the quartz movement. This automatic quartz arrangement provides the accuracy of a quartz movement without the need for routine battery replacement. An alternative power source with functionally similar results is a photoelectric cell ("solar watch").

QMRThe Quartz Crisis, (also known as the Quartz Revolution),[1][2] is a term used in the watchmaking industry to refer to the economic upheavals caused by the advent of quartz watches in the 1970s and early 1980s, which largely replaced mechanical watches.

It caused a decline of the Swiss watchmaking industry, which chose to remain focused on traditional mechanical watches, while the majority of world watch production shifted to Asian companies that embraced the new technology.

Swiss hegemony[edit]

The first Swiss quartz clock, which was made after WW II (left), on display at the International Watchmaking Museum in La Chaux-de-Fonds.

During World War II, Swiss neutrality permitted the watch industry to continue making consumer time keeping apparatus while the major nations of the world shifted timing apparatus production to timing devices for military ordnance. As a result, the Swiss watch industry enjoyed an effective monopoly. The industry prospered in the absence of any real competition. Thus, prior to the 1970s, the Swiss watch industry had 50% of the world watch market.[3]

In the early 1950s a joint venture between the Elgin Watch Company in the United States and Lip of France to produce an electromechanical watch – one powered by a small battery rather than an unwinding spring – laid the groundwork for the quartz watch.[4] Although the Lip-Elgin enterprise produced only prototypes, in 1957 the first battery-driven watch in production was the American-made Hamilton 500.

In 1954, Swiss engineer Max Hetzel developed an electronic wristwatch that used an electrically charged tuning fork powered by a 1.35 volt battery. The tuning fork resonated at precisely 360 Hz and it powered the hands of the watch through an electro-mechanical gear train. This watch was called the Accutron and was marketed by Bulova, starting in 1960. Although Bulova did not have the first battery powered wristwatch, the Accutron was a powerful catalyst, as by that time the Swiss watch manufacturing industry was a mature industry with a centuries-old global market and deeply entrenched patterns of manufacturing, marketing and sales.

In 1962, the Centre Electronique Horloger (CEH) was established in Neuchâtel to develop a Swiss-made quartz wristwatch, while simultaneously in Japan, Seiko was also working on an electric watch and developing quartz technology.[5]

Technological revolution[edit]

Main article: Quartz clock

In the late 1950s and early 1960s, both Seiko and a consortium of Switzerland's top firms competed to develop the first quartz wristwatch. One of the first successes was a portable quartz clock called the Seiko Crystal Chronometer QC-951. This portable clock was used as a backup timer for marathon events in the 1964 Summer Olympics in Tokyo. In 1966 prototypes of the world's first quartz pocketwatch were unveiled by Seiko and Longines in the Neuchâtel Observatory's 1966 competition.[6]

On 25 December 1969, Seiko unveiled the quartz Astron, the world's first quartz watch.[6][7] The first Swiss quartz analog watch—the Ebauches SA Beta 21 containing the Beta 1 movement—arrived at the 1970 Basel Fair.[6][8] The Beta 21 was released by numerous manufacturers including the Omega Electroquartz.

On 6 May 1970, Hamilton introduced the Pulsar - the world's first electronic digital watch.[9]

In 1974 Omega introduced the Omega Marine Chronometer, the first watch ever to be certified as a Marine Chronometer, accurate to 12 seconds per year using a quartz circuit that produces 2,400,000 vibrations per second.

In 1976 Omega introduced the Omega Chrono-Quartz, the world's first analogue/digital chronograph, which was succeeded within 12 months by the Calibre 1620, the company's first completely LCD chronograph wristwatch.

The rise of quartz in the 1970s[edit]

Seiko Grand Quartz, produced in 1978.

Despite these dramatic advancements, the Swiss hesitated in embracing quartz watches. At the time, Swiss mechanical watches dominated world markets. In addition, excellence in watchmaking was a large component of Swiss national identity. From their position of market strength, and with a national watch industry organized broadly and deeply to foster mechanical watches, many in Switzerland thought that moving into electronic watches was unnecessary. Others outside of Switzerland, however, saw the advantage and further developed the technology,[10] and by 1978 quartz watches overtook mechanical watches in popularity, plunging the Swiss watch industry into crisis while at the same time strengthening both the Japanese and American watch industries. This period of time was marked by a lack of innovation in Switzerland at the same time that the watch-making industries of other nations were taking full advantage of emerging technologies, specifically quartz watch technology, hence the term Quartz Crisis.

As a result of the economic turmoil that ensued, many once-profitable and famous Swiss watch houses became insolvent or disappeared. This period of time completely upset the Swiss watch industry both economically and psychologically. During the 1970s and early 1980s, technological upheavals, i.e. the appearance of the quartz technology, and an otherwise difficult economic situation resulted in a reduction in the size of the Swiss watch industry. Between 1970 and 1988, Swiss watch employment fell from 90,000 to 28,000.[6]

Outside of Switzerland, the crisis is often referred to as the Quartz Revolution, particularly in the United States where many American companies had gone out of business or had been bought out by foreign interests by the 1960s. When the first quartz watches were introduced in 1969, the United States promptly took a technological lead in part due to microelectronics research for military and space programs. It was American companies like Texas Instruments, Fairchild, and National Semiconductor, who started the mass production of digital quartz watches and made them affordable.[1] It did not remain so forever; by 1978 Hong Kong exported the largest number of electronic watches worldwide, and US semiconductor companies came to pull out of the watch market entirely. With the sole exception of Timex, the remaining traditional American watch companies, including Hamilton, went out of business and sold their brand names to foreign competitors.[11]

The renaissance, the Swatch, and the future of timekeeping[edit]

Main article: Swatch

Swatch Once Again watch

By 1983, the crisis reached a critical point. The Swiss watch industry, which had 1,600 watchmakers in 1970, had now declined to 600.[12] A research consortium, the Swiss ASUAG group (Société Générale de l'Horlogerie Suisse SA), was formed to save the industry and the result was launched in March 1983 – the Swatch. The Swatch would be instrumental in reviving the Swiss watch industry giving a new bill of health to all brands concerned and gave rise to what would become the Swatch Group – the largest watch manufacturer in the world.[13] The Swatch was sealed in a plastic case, sold as a disposable commodity with little probability of repair, and had a small number of moving parts (51) compared to about 91 for mechanical watches. Furthermore, production was essentially automated, which resulted in a higher profitability.[14] The Swatch was a huge success; in less than two years, more than 2.5 million Swatches were sold.[5]

The larger global market still largely reflected other trends, however. In the US domestic market, for example, the Swatch was something of a 1990s fad resting largely on variety of colors and patterns, and the bulk of production still came from offshore sites such as China and Japan, in digitally-dominated or hybrid brands like Casio, Timex, and Armitron. Paradoxically, the quartz revolution drove many Swiss manufacturers to seek refuge in (or be winnowed out to) the higher end of the market, such as Rolex, Patek Philippe, and the like. A few brands[examples needed] aimed further up in the midrange toward prices of hundreds of dollars but still avoided the realm of the high end mechanicals, which might run from several thousand dollars into the hundreds of thousands dollars.[citation needed]

QMRThe Omega Chrono-Quartz was the world’s first digital/ analogue chronograph. It was invented by Omega SA. The watch launched at the 1976 Montreal Olympic Games and was Omega's flagship chronograph at that time. The watch is noteworthy as it was the first chronograph wristwatch in the world to combine analogue display for the time functions and a digital display for the chronograph function, each working independently of one another but running on the same quartz resonator. (32 kHz) [1][2]

Famous owners include NASA astronaut Charles Duke, famous cyclist and tour de France competitor Bert Oosterbosch and in recent years British motoring journalist James May.

Early development[edit]

The 1970s was a period of rapid development in quartz watch technology, between 1970 and 1980 the quartz era had taken hold of the entire watch making industry and never was there a time in watch making history that technology developed so quickly.

Omega calibre 1611 Chrono-Quartz movement

Omega were at the forefront of quartz wristwatch development in Switzerland, they had already introduced the Omega Electroquartz as the first Swiss production watch and the Omega Marine Chronometer as the first wristwatch to gain certification as a Marine Chronometer (and was accurate to 1 second per month).

As liquid crystal display technology began to be integrated into quartz wristwatches Omega saw an opportunity to again develop another world first by integrating an LCD display into an analogue watch.

The calibre 1611 ‘Albatross’ (designated so because of the shape of the battery clamping system resembling an albatross's wings) was designed by Raymond Froidevaux. The movement had one large circuit on the rear of the watch which controlled both the analogue movement (based on calibre 1320) [3] and digital LCD elements. The Chrono Quartz was originally ran on two mercury 323 running time of 26 months, this was replaced by the silver oxide battery 393 running time 15 months. The watch was not designed for intricate repair but more as a modular system, which would be replaced dependent on the components required. Working versions of the watch were available in 1975 but Omega did not release the watch until 1976.[4]

Production watch[edit]

Omega calibre 1611 Chrono-Quartz case back with olympic logo

The Omega Chrono-Quartz is rare amongst modern wristwatches as the calibre 1611 was only used on one single watch; the watch was only made in 15,000 units.[5]

The production watch was released at the 1976 Montreal Olympic Games and at the same time Omega sponsored the event and the main Olympic scoreboard bore remarkable similarities to the Chrono-Quartz wrist watch.

The design of the watch was very distinctive, primarily it was large (51mm wide including the pushers), even in comparison to other watches of the day, constructed in stainless steel and with an integral solid link stainless steel bracelet. The watch has a significant wrist presence. The main reason for the big dimensions was the size of the movement, which had to accommodate the analogue module (on the right) and the digital chronograph module (on the left). The case back bore the Omega Seamaster hippocampus as well as the Olympic crest in recognition of the event at which it was released.

The chronograph module was controlled by three round pushers on the left side of the case and the analogue time and date was adjusted by a crown which could be pulled out to adjust the hour and date and a button within the crown which when pressed advanced the minutes.

When new in 1976 the watch was £375, by contrast Omegas establish Chronograph the Speedmaster professional 145.022 was £175, this made the Chrono-Quartz a very expensive option in comparison to the other chronographs in Omegas range. This was one of Omega's range of one year only production chronographs, which included the famous Omega Speedmaster 125 and the Omega Bullhead of 1969.

Summary[edit]

Omega calibre 1611 Chrono-Quartz

Although revolutionary in design and function the reign of the Chrono-Quartz as Omega's flagship chronograph was short lived. In 1977 Omega released the calibre 1620, which was a full digital LCD chronograph in numerous executions of Constellation and Speedmaster Professional. The fully LCD omega Chronograph rendered the Chrono-Quartz obsolete, at the same time changes in design and fashion moved towards slimmer and smaller watches, by comparison the 1620 range of watches was at least 1/3rd smaller than the bulky Chrono-Quartz.[6]

The Chrono-Quartz remained in Omega's line up for a further two years but by 1979 had been completely phased out. Despite its relatively short production span and limited application the Chrono-Quartz represents one of Omega's most distinctive designs of the 1970s and was a world first in blending analogue and digital technology, which was also later used by Heuer amongst others and is still used by modern wristwatch manufacturers.

Chrono-Quartz watches are becoming collectible and examples in excellent original condition are fetching premiums in excess of $1500 – $2000, condition of the watches is important as spares such as circuits and motors are become sought after and servicing can become expensive if new parts are required.

QMROmega Electroquartz

From Wikipedia, the free encyclopedia

The Omega Electroquartz was introduced in 1969 as the first production Swiss quartz watch. It was the collaboration of 20 Swiss watch companies and the movement was utilised by Rolex, Patek Phillipe and Omega SA amongst others. The Beta 21 movement used in the Electroquartz was accurate to 5 seconds per month, far better than any automatic or manual wind movement of the day.

Introduction[edit]

The Omega Electroquartz was the first Swiss quartz watch produced as part of a range called beta 21 watches, the beta 21 was developed at CEH research laboratory by twenty Swiss watch manufacturers. The first production watches were introduced to the market in 1970 very shortly after the first quartz watch, the Seiko 35 SQ Astron in December 1969. The beta 21 is noteworthy and significantly important to the history of watch making as it marked the first quartz watch produced on an industrial level and began what has now come to be known in the watchmaking world as the quartz crisis

Numerous Swiss manufacturers released beta 21 watches, the first Rolex Oysterquartz model used the beta 21 movement, Patek Philippe also produce a range of beta 21 models as did the International Watch Company including it in their first Davinci watch.[1]

By far the largest supplier of beta 21 and subsequent beta 22 watches was Omega SA, who produced circa 10,000 Electroquartz watches between 1970 and 1977

Early development[edit]

Csem-beta1

In 1966 after six years of research at Centre Electronique Horloger laboratories in Neuchâtel (CEH), Switzerland the first prototype of a quartz wristwatch was produced, the beta-1, this was the first real quartz wristwatch and operated using an 8192 Hz quartz oscillator, which was mounted to an in-house integrated circuit.[2]

In 1967 the beta-2 was tested and was awarded 'Concours Chronométrique International de l'Observatoire de Neuchâtel' setting a new record for wristwatch accuracy over the test period of 0.003 seconds per day, by contrast even the best chronometers of the day were accurate to around 3–10 seconds per day.[3]

In 1969, two years after the beta-2 tests twenty Swiss watch companies agreed to manufacture 6000 of the beta 21 production watches produced on an industrial level.

In late 1969 a few hundred beta 21 units were produced to exhibit from a range of the agreed manufacturers at the 1970 Basel Fair. These production watches were accurate to 5 seconds per month, far better than any automatic or manual wind chronometer at the time and an enormous leap in accurate time keeping. The movement was a modular design and components were manufactured by individual companies (such as Omega who made the micro motor) and then assembled at three workshops.[4]

The beta 21 watches had a sweeping second hand, which moved smoothly round the dial and ‘hummed’ thanks to the Omega vibrating micro motor.

Production watches[edit]

Electroquartz first generation stainless steel and 18-carat gold

Although 20 watch companies were originally involved in the development of the beta 21 production watch under CEH, not all of these companies took this to production stage. It is indicated that 18 Swiss manufacturers showed beta 21 watches at the 1970 Basel Fair.[5]

Between 1970 and 1971 6000 beta 21 units were manufactured (Omega’s calibre was 1300).

To date there are only known of surviving examples from 12 of the original manufacturers and a number of these are not complete watches:

Omega Electroquartz date and non date movements front

Omega Electroquartz date and non date movements rear

1. Bucherer : Branded as Bucherer Quartz and available in 18-carat gold or stainless steel models.

2. Bulova:Branded as Accuquartz, available in an 18-carat gold models.

3. Favre-Leuba: This has only ever been seen as a movement with dial and not as a production watch.

4. International Watch Company: Branded as Davinci, International and also as a pocket watch available in a range of precious metals and stainless steel.

5. Jaeger-lecoultre: Branded as Masterquartz however this has only ever been seen as a movement with dial and not as a production watch.

6. Omega SA: Branded as Electroquartz and available in 18-carat gold and stainless steel models [6]

7: Longines: Branded as Quartz-Chron, this has only ever been seen as a single production watch in stainless steel.

8. Patek Philippe: Branded as Cercle d'Or available in 18-carat gold models.

9. Piaget: Available in 18-carat gold as date and non date models.

10. Rado: Branded as Quartz 8192, available in Stainless steel and made circa 400 examples.

11. Rolex: Branded as Oysterquartz calibre 5100 available in 18-carat gold.

12. Zenith: This has only ever been seen as a movement without dial and not as a production watch.

Omega's version of the beta 21 wristwatch came in the form of the Electroquartz, the case design was larger at the top than the bottom and as such it gained the nickname 'pupitre' after the French word for writing desk. Omega took 5 examples of the electroquartz to the 1970 Basel Fair in 18-carat gold with integral bracelet and displayed them in a row running continually at exactly the same time to demonstrate their accuracy, they sold all five examples at the Basel Fair.[7]

Shortly after the 1970 fair the Electroquartz became commercially available to the public in 18-carat gold and Stainess Steel, both with the pupitre case design at a cost of £1150 in 18-carat yellow gold with integral bracelet and £330 in Stainless steel on bracelet, by contrast the Moonwatch on bracelet was £93.50 and the now coveted Omega Bullhead was only £90.50.

Further developments[edit]

According to records between 1972 and 1974 50,000 beta 22’s were produced [8] (Omega’s calibres were 1301 and 1302), although only a tiny number of these appear to have ever made it to production watches based on the availability of used examples now. The beta 22 was a development of the beta 21 available in date and non date models with refined quartz circuits.

Electroquartz 2nd generation 18-carat gold

Rolex and Patek Philippe as well as IWC and Piaget (amongst others in the original group) produced very small numbers of beta 21/22 watches and towards the mid part of the 1970s all were moving away from the beta 21/22 movement (because of their cost, including the massive R&D costs) and towards more modern quartz technology, including Rolex developing their own in house Oysterquartz movement, which remained in production from 1977 until 2001.

Omega SA made the most use of the beta 21 and beta 22 calibre and kept it in their range of watches until circa 1977. Throughout this period of time Omega produced a number of variations of the Electroquartz Constellation wristwatch, most famously the pupitre but also in a rectangular case in Stainless steel as well as other date and non date models.

Omega's experimentation with case design throughout the 1970s was never more obvious than in the Electroquartz range of watches, there were numerous case executions, many of the later calibre 1301 and 1302 examples being made in 18-carat yellow or white gold. Omega's range of watches during the 1970s was extensive and included usually three or four Electroquartz variations every year, although they competed with the wider range of Omega products including other quartz watches like the Megaquartz series, the majority of them were precious metal and as such were priced towards the very top end of the Omega line up. The pictured 18-carat non date example sourced by UK collector by Thomas Dick retailed when new in 1974 for £2006 sterling, by contrast Omegas then flagship chronograph, the limited edition Speedmaster 125 retailed for £186.50.

Omega Electroquartz clock[edit]

In addition to the beta 21 Electroquartz watches Omega also developed an 8192 Hz Electroquartz clock, this was Omega SA's first quartz production quartz clock and used a thermo-compensated quartz bar and integrated circuit, produced in very small numbers under caliber 1390.

EQ clock

The quartz clock was supplied in a stylish grey Cycolac resin case, because of the size and complexities of the movement the clock was quite large and weighed in at over 1 kilo.

The clock runs on 4 AA type batteries and has an accuracy of circa 12 seconds per year. It features time and date and has a lever for manually trimming the seconds without interfering with the operation of the watch.[9]

There are very few remaining examples of these clocks, other than those on display at the Omega museum in Bienne and Swiss Time Services in the UK, and there are less than 10 known examples in private collections. The pictured clock (owned by Omega collector Thomas Dick) is serviced and working correctly and is accurate to 12 seconds per year, which is within specification of +/- 1 second per month when kept at a constant temperature of between 10 °C and 30 °C.

Summary[edit]

Omega Electroquartz generation 1 and 2 compared to Omega Dinosaur, watches sourced by Thomas Dick

Omega Electroquartz / Dinosaur comparison

Despite the significance of the beta 21 series of watches unfortunately the speed of development of quartz wristwatches during the 1970s as well as the influx of reliable quartz technology from Japan and the US meant that the beta 21 and beta 22 wristwatches became obsolete almost as they came into initial production.

Omega's development of their own in house Megaquartz range of watches developed by SSIH included the reliable 32 kHz lines (accurate to 5 seconds per month) as well as their flagship Omega Marine Chronometer (accurate to 12 seconds per year) [10] rendered even Omegas efforts to reap their investment very difficult.

By the end of the 1970s and into the early 1980s the industry had made such advances in quartz watch technology that Omega were producing 18-carat models which were less than 2mm thick (the dinosaur) which were accurate to 5 seconds per month, as shown in the attached image of watches sourced by Omega collector Thomas Dick, which is a stark demonstration of how far quartz technology watches had progressed in less than a decade.

Within ten years of the introduction of the beta 21 the Swiss watch industry was in a quartz crisis. Technology had developed so quickly that quartz movements had become smaller, thinner, more accurate and more reliable whilst being significantly cheaper to manufacture. The influx of cheap, well-made and reliable quartz watches from non Swiss manufacturers mixed with the lack of progress made by the majority of the Swiss watch making industry led to the demise of numerous manufacturers and nearly toppled giants like Omega.

Today beta 21 and beta 22 watches are becoming very collectible, with Rolex and Patek Phillipe examples in precious metals fetching $20000+, the majority of readily available examples are Omega with prices starting at around $500 for an average working stainless steel example and rising dependent on the model, rarity and metal. These early quartz watches are proving a sound investment for collectors and are without doubt one of the more important developments in wristwatch technology of the 20th century.

QMROmega Marine Chronometer

From Wikipedia, the free encyclopedia

OMC calibre 1516

The Omega Marine Chronometer was the first quartz wristwatch ever to be awarded certified status as a Marine Chronometer. The watch was made by Omega SA and developed by John Othenin-Girard and is one of the most accurate non thermo-compensated production watches ever made, keeping time to within 1 second per month [1]

Introduction[edit]

The watch was introduced to the market in 1974 under calibre 1511, having an unrivalled accuracy of 12 seconds per year thanks to the revolutionary 2.4 MHz quartz circuit.[2] in 1976 the calibre 1516 Marine Chronometer was introducedwith smaller case dimensions and altered movement, although performance remained the same, sales began in 1974 and the watch remained in Omega line up until 1978.

Famous owners of Omega Marine Chronometers have included Jaques Cousteau and Eric Tabarly

Early development[edit]

The first prototypes of the ‘1500 family’ quartz watch (which later developed into the Marine Chronometer) were presented at the Basel Fair in 1970 as calibre 1500, developed by Omega and the Battelle Geneva Research Institute. Known as the ‘Elephant’, there are rumored to have been only five examples of this watch made by Omega.[3][4]

OMC prototype 1

The calibre 1500 ‘Elephant’ (known so because of the design of the movement with two large battery compartments resembling large ears) boasted an accuracy of 12 seconds per year, which equated to 1 second per month, five times more accurate than the beta 21 (the first Swiss production quartz watch) introduced to the market the year previous. The calibre 1500 was Omega’s first in-house quartz movement developed under project leader John Othenin-Girard by SSIH.[5]

OMC prototype 2

The development of the calibre 1500 and subsequent successors cost Omega 30 million Swiss Francs with the sole intention to produce a wristwatch of unparalleled accuracy and performance. This significantly improved performance in time keeping was to be achieved by the development of a circular quartz resonator that vibrated at 2,359,356 times per second,[6] by comparison the Beta 21 quartz resonator (which as a watch had an accuracy of 5 seconds per month) vibrated at 8192 times per second. The lenticular crystal oscillator in the calibre 1500, 1510, 1511 and 1516 was developed in the UK and used solely in the Megaquartz calibre 2400 series.

The five calibre 1500 watches produced achieved the required 1 second per month accuracy through a stable (non thermo compensated) quartz resonator as part of an integrated circuit which divided the huge frequency to produce pulses which ran the electromagnetic motor. These watches were the first to feature a time zone adjuster, which allowed the hour to be adjusted without interfering with the minute or second hand, this is a feature, followed through into the production watch alongside the later introduction of a second trimmer.[7]

The design of the calibre 1500 was modular, which translated into the production watch, however the movement design and layout of the final calibre 1511 and subsequent calibre 1516 was completely different. One of the major flaws of the calibre 1500 was battery consumption (from the twin cells), although untested until recently when one of the prototypes came to market as a running watch in 2011. The owner, Omega collector Thomas Dick,[8] tested the watch and concluded that the battery life of the twin (344) cells was approximately 5 weeks, however the accuracy when bench tested was 0.03 seconds per day, still equating to 12 second per year.

There were numerous other prototypes of the calibre 1510 watches, most of which were around case design, there are a number in private hands as well as a selection of prototype case designs and dial variations at the Omega museum in Bienne, Switzerland. These prototype watches were no calibre variations but alternative designs for cases and dials which ultimately led to the production watch.

.19 MHz Ships Marine Chronometer[edit]

In addition to the Marine Chronometer watches Omega also developed a Marine Chronometer clock using an advanced 4.19 MHz quartz resonator giving an unparalleled accuracy of less than 5 seconds per year under calibre 1525. The clock was designed at the request of the French Navy tested for over a year by their Hydrographic and Oceanographic service SHOM.[12]

OMC ships clock

This ships clock was available commercially at great expense but was predominantly used for military application with the French Navy, who used the Marine Chronometer clock in the majority of their fleet.

The clock was supplied in a mahogany box with brass fitting and was very much a case of function over form and built to the highest of military specifications including anti magnetic shielding. The clocks were all individually numbered on a brass plaque and ran on 2 AA type batteries, three of which ran the clock and a fourth was used as a back up power source when changing the other batteries and standard running time for a set of batteries was circa 3 years.

The 4.19 MHz technology was also used in Omega's range of LED timing equipment and prototyped in a wristwatch. The main movement of the watch was based on an Omega calibre 1343 Elan series but designated as 1522 it utilised a revolutionary 4.19 MHz micro quartz circuit, however there are only two known operational prototype,one of which is now in the hands of a US collector and the other is in a collection in Hong Kong.

Summary[edit]

In total Omega produced a rumored 10,000 calibre 1500 family watches (around 2000 were in spares), although revolutionary their cost was prohibitive and with the speed of development of quartz during the 1970s Omega wrote off much of the original R&D costs and towards the end of their production run Omega offered the remaining examples to Omega employees at 350 Swiss Francs, 1/10th of the retail cost .[13]

The Marine Chronometers and non Marine Chronometer calibre 1510 watches remain amongst the most significantly important Omegas ever made, one of the earliest quartz watches produced with an excellent accuracy, and to this day a serviced example will still be accurate to 1 second per month.[14]

QMRPulsar quartz chronograph

QMRPulsar is a brand of watch and a division of Seiko Watch Corporation of America (SCA). While Pulsar was the world's first electronic digital watch, today Pulsar watches are usually analog. They generally use the same movements as the lower-end Seikos such as the 7T62 quartz chronograph movement.

QMRThe Astron wristwatch, formally known as the Seiko Quartz-Astron 35SQ, was the world's first "quartz clock" wristwatch, i.e., one based on a quartz crystal oscillator. It is now registered on the List of IEEE Milestones as a key advance in electrical engineering.

The Astron was unveiled in Tokyo on December 25, 1969, after ten years of research and development at Suwa Seikosha (currently named Seiko Epson), a manufacturing company of Seiko Group. Within one week 100 gold watches had been sold, at a retail price of 450,000 yen (US$1,250) each (at the time, equivalent to the price of a medium-sized car).[1] Essential elements included a Y-type quartz oscillator of 8192 cps, a hybrid integrated circuit, and a phase locked ultra-small stepping motor to turn its hands. The Astron was accurate to ±0.2 seconds per day, ±5 seconds per month, or one minute per year.

Anniversaries[edit]

In March 2010, at the BaselWorld watch fair and trade show in Switzerland, Seiko previewed a limited edition new version and related designs of the original Astron watch, commemorating the fortieth anniversary in December 2009 of the debut of the Astron watch.[2]

QMRThe Pierce oscillator is a type of electronic oscillator particularly well-suited for use in piezoelectric crystal oscillator circuits. Named for its inventor, George W. Pierce (1872-1956),[1][2] the Pierce oscillator is a derivative of the Colpitts oscillator. Virtually all digital IC clock oscillators are of Pierce type, as the circuit can be implemented using a minimum of components: a single digital inverter, two resistors, two capacitors, and the quartz crystal, which acts as a highly selective filter element. The low manufacturing cost of this circuit, and the outstanding frequency stability of the quartz crystal, give it an advantage over other designs in many consumer electronics applications.

QMRSilicon dioxide, also known as silica (from the Latin silex), is a chemical compound that is an oxide of silicon with the chemical formula SiO2. It has been known since ancient times. Silica is most commonly found in nature as quartz, as well as in various living organisms.[5][6] In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing both as several minerals and being produced synthetically. Notable examples include fused quartz, crystal, fumed silica, silica gel, and aerogels. Applications range from structural materials to microelectronics to components used in the food industry

Production[edit]

Silicon dioxide is mostly obtained by mining and purification of quartz. Quartz comprises more than 10% by mass of the earth's crust.[7] This product will be suitable for many purposes while for others chemical processing will be required to make a purer or otherwise more suitable (e.g. more reactive or fine-grained) product.

Fumed silica[edit]

Main article: Fumed silica

Pyrogenic silica (sometimes called fumed silica or silica fume) is a very fine particulate or colloidal form of silicon dioxide. It is prepared by burning SiCl4 in an oxygen rich hydrocarbon flame to produce a "smoke" of SiO2.[8]

SiCl4 + 2 H2 + O2 → SiO2 + 4 HCl.

Silica fume[edit]

Main article: Silica fume

This product is obtained as byproduct from hot processes like ferro-silicon production. It is less pure than fumed silica and should not be confused with that product. The production process, particle characteristics and fields of application of fumed silica are all different from those of silica fume.

Precipitated silica[edit]

Main article: Precipitated silica

Amorphous silica, silica gel, is produced by the acidification of solutions of sodium silicate. The gelatinous precipitate is first washed and then dehydrated to produce colorless microporous silica.[8] Idealized equation involving a trisilicate and sulfuric acid is shown:

Na2Si3O7 + H2SO4 → 3 SiO2 + Na2SO4 + H2O

Approximately one billion kilograms/year (1999) of silica was produced in this manner, mainly for use for polymer composites – tires and shoe soles.[7]

On microchips[edit]

Thin films of silica grow spontaneously on silicon wafers via thermal oxidation. This route gives a very shallow layer (approximately 1 nm or 10 Å) of so-called native oxide.[9] Higher temperatures and alternative environments are used to grow well-controlled layers of silicon dioxide on silicon, for example at temperatures between 600 and 1200 °C, using so-called dry or wet oxidation with O2 or H2O, respectively.[10] The depth of the layer of silicon replaced by the dioxide is 44% of the depth of the silicon dioxide layer produced.[10]

The native oxide layer can be beneficial in microelectronics, where it acts as electric insulators with high chemical stability. In electrical applications, it can protect the silicon, store charge, block current, and even act as a controlled pathway to limit current flow.[11]

Laboratory or specialty methods[edit]

From silicate esters[edit]

Many routes to silicon dioxide start with silicate esters, the best known being tetraethyl orthosilicate (TEOS). Simply heating TEOS at 680–730 °C gives the dioxide:

Si(OC2H5)4 → SiO2 + 2 O(C2H5)2

Similarly TEOS combusts around 400 °C:

Si(OC2H5)4 + 12 O2 → SiO2 + 10 H2O + 8 CO2

TEOS undergoes hydrolysis via the so-called sol-gel process. The course of the reaction and nature of the product are affected by catalysts, but the idealized equation is:[12]

Si(OC2H5)4 + 2 H2O → SiO2 + 4 HOCH2CH3

Other methods[edit]

Being highly stable, silicon dioxide arises from many methods. Conceptually simple, but of little practical value, combustion of silane gives silicon dioxide. This reaction is analogous to the combustion of methane:

SiH4 + 2 O2 → SiO2 + 2 H2O.

Uses[edit]

An estimated 95% of silicon dioxide produced is consumed in the construction industry, e.g. for the production of Portland cement.[7] Other major applications are listed below.

Precursor to glass and silicon[edit]

Silica is used primarily in the production of glass for windows, drinking glasses, beverage bottles, and many other uses. The majority of optical fibers for telecommunication are also made from silica. It is a primary raw material for many ceramics such as earthenware, stoneware, and porcelain.

Silicon dioxide is used to produce elemental silicon. The process involves carbothermic reduction in an electric arc furnace:[13]

SiO2 + 2 C → Si + 2 CO

Major component used in sand casting[edit]

Silica, in the form of sand is used as the main ingredient in sand casting for the manufacture of a large number of metallic components in engineering and other applications. The high melting point of silica enables it to be used in such applications.

Food and pharmaceutical applications[edit]

Silica is a common additive in the production of foods, where it is used primarily as a flow agent in powdered foods, or to adsorb water in hygroscopic applications. It is the primary component of diatomaceous earth. Colloidal silica is also used as a wine, beer, and juice fining agent.[7]

In pharmaceutical products, silica aids powder flow when tablets are formed.

Other[edit]

A silica-based aerogel was used in the Stardust spacecraft to collect extraterrestrial particles. Silica is also used in the extraction of DNA and RNA due to its ability to bind to the nucleic acids under the presence of chaotropes. Hydrophobic silica is used as a defoamer component. In hydrated form, it is used in toothpaste as a hard abrasive to remove tooth plaque.

In its capacity as a refractory, it is useful in fiber form as a high-temperature thermal protection fabric. In cosmetics, it is useful for its light-diffusing properties and natural absorbency. It is also used as a thermal enhancement compound in ground source heat pump industry.

QMR A QAPF diagram is a double triangle diagram which is used to classify igneous rocks based on mineralogic composition. The acronym, QAPF, stands for "Quartz, Alkali feldspar, Plagioclase, Feldspathoid (Foid)". These are the four mineral groups used for classification in QAPF diagram. Q, A, P and F percentages are normalized (recalculated so that their sum is 100%).

QMRFeldspars (KAlSi3O8 – NaAlSi3O8 – CaAl2Si2O8) are a group of rock-forming tectosilicate minerals that make up as much as 60% of the Earth's crust.[2]

Feldspars crystallize from magma as veins in both intrusive and extrusive igneous rocks and are also present in many types of metamorphic rock.[3] Rock formed almost entirely of calcic plagioclase feldspar (see below) is known as anorthosite.[4] Feldspars are also found in many types of sedimentary rocks.[5]

Compositions[edit]

This group of minerals consists of framework tectosilicates. Compositions of major elements in common feldspars can be expressed in terms of three endmembers:

Potassium-Feldspar (K-spar) endmember KAlSi3O8[2]

Albite endmember NaAlSi3O8[2]

Anorthite endmember CaAl2Si2O8[2]

Solid solutions between K-feldspar and albite are called alkali feldspar.[2] Solid solutions between albite and anorthite are called plagioclase,[2] or more properly plagioclase feldspar. Only limited solid solution occurs between K-feldspar and anorthite, and in the two other solid solutions, immiscibility occurs at temperatures common in the crust of the earth. Albite is considered both a plagioclase and alkali feldspar.

Alkali feldspars[edit]

The alkali feldspars are as follows:

orthoclase (monoclinic)[7]—KAlSi3O8

sanidine (monoclinic)[8]—(K,Na)AlSi3O8

microcline (triclinic)[9]—KAlSi3O8

anorthoclase (triclinic)—(Na,K)AlSi3O8

Sanidine is stable at the highest temperatures, and microcline at the lowest.[7][8] Perthite is a typical texture in alkali feldspar, due to exsolution of contrasting alkali feldspar compositions during cooling of an intermediate composition. The perthitic textures in the alkali feldspars of many granites can be seen with the naked eye.[10] Microperthitic textures in crystals are visible using a light microscope, whereas cryptoperthitic textures can be seen only with an electron microscope.

Barium feldspars[edit]

Barium feldspars are also considered alkali feldspars. Barium feldspars form as the result of the substitution of barium for potassium in the mineral structure. The barium feldspars are monoclinic and include the following:

celsian—BaAl2Si2O8[11]

hyalophane—(K,Ba)(Al,Si)4O8[12]

Plagioclase feldspars[edit]

The plagioclase feldspars are triclinic. The plagioclase series follows (with percent anorthite in parentheses):

albite (0 to 10)—NaAlSi3O8

oligoclase (10 to 30)—(Na,Ca)(Al,Si)AlSi2O8

andesine (30 to 50)—NaAlSi3O8—CaAl2Si2O8

labradorite (50 to 70)—(Ca,Na)Al(Al,Si)Si2O8

bytownite (70 to 90)—(NaSi,CaAl)AlSi2O8

anorthite (90 to 100)—CaAl2Si2O8

Intermediate compositions of plagioclase feldspar also may exsolve to two feldspars of contrasting composition during cooling, but diffusion is much slower than in alkali feldspar, and the resulting two-feldspar intergrowths typically are too fine-grained to be visible with optical microscopes. The immiscibility gaps in the plagioclase solid solutions are complex compared to the gap in the alkali feldspars. The play of colours visible in some feldspar of labradorite composition is due to very fine-grained exsolution lamellae.

QMRSilicate minerals

From Wikipedia, the free encyclopedia

(Redirected from Tectosilicate)

Silicate minerals

Chrysocolla.jpg

Copper silicate mineral chrysocolla

Category Mineral

"Orthosilicate" redirects here. For anion, see Orthosilicate (ion).

The silicate minerals are rock-forming minerals, constituting approximately 90 percent of the crust of the Earth. They are classified based on the structure of their silicate group which contain different ratios of silicon and oxygen. They make up the largest and most important class of rock-forming minerals.

Nesosilicates or orthosilicates[edit]

Basic (ortho-)silicate anion structure

Nesosilicate specimens at the Museum of Geology in South Dakota

Main category: Nesosilicates

Nesosilicates (from Greek νησος nēsos, island), or orthosilicates, have the orthosilicate ion, which constitute isolated (insular) [SiO4]4− tetrahedra that are connected only by interstitial cations. Nickel-Strunz classification: 09.A

Phenakite group

Phenakite - Be2SiO4

Willemite - Zn2SiO4

Olivine group

Forsterite - Mg2SiO4

Fayalite - Fe2SiO4

Tephroite - Mn2SiO4

Garnet group

Pyrope - Mg3Al2(SiO4)3

Almandine - Fe3Al2(SiO4)3

Spessartine - Mn3Al2(SiO4)3

Grossular - Ca3Al2(SiO4)3

Andradite - Ca3Fe2(SiO4)3

Uvarovite - Ca3Cr2(SiO4)3

Hydrogrossular - Ca3Al2Si2O8(SiO4)3-m(OH)4m

Zircon group

Zircon - ZrSiO4

Thorite - (Th,U)SiO4

Kyanite crystals (unknown scale)

Al2SiO5 group

Andalusite - Al2SiO5

Kyanite - Al2SiO5

Sillimanite - Al2SiO5

Dumortierite - Al6.5-7BO3(SiO4)3(O,OH)3

Topaz - Al2SiO4(F,OH)2

Staurolite - Fe2Al9(SiO4)4(O,OH)2

Humite group - (Mg,Fe)7(SiO4)3(F,OH)2

Norbergite - Mg3(SiO4)(F,OH)2

Chondrodite - Mg5(SiO4)2(F,OH)2

Humite - Mg7(SiO4)3(F,OH)2

Clinohumite - Mg9(SiO4)4(F,OH)2

Datolite - CaBSiO4(OH)

Titanite - CaTiSiO5

Chloritoid - (Fe,Mg,Mn)2Al4Si2O10(OH)4

Mullite (aka Porcelainite) - Al6Si2O13

Sorosilicates[edit]

Sorosilicate exhibit at Museum of Geology in South Dakota

Main category: Sorosilicates

Sorosilicates (from Greek σωρός sōros, heap, mound) have isolated double tetrahedra groups with (Si2O7)6− or a ratio of 2:7. Nickel-Strunz classification: 09.B

Hemimorphite (calamine) - Zn4(Si2O7)(OH)2·H2O

Lawsonite - CaAl2(Si2O7)(OH)2·H2O

Ilvaite - CaFe2+2Fe3+O(Si2O7)(OH)

Epidote group (has both (SiO4)4− and (Si2O7)6− groups)

Epidote - Ca2(Al,Fe)3O(SiO4)(Si2O7)(OH)

Zoisite - Ca2Al3O(SiO4)(Si2O7)(OH)

Clinozoisite - Ca2Al3O(SiO4)(Si2O7)(OH)

Tanzanite - Ca2Al3O(SiO4)(Si2O7)(OH)

Allanite - Ca(Ce,La,Y,Ca)Al2(Fe2+,Fe3+)O(SiO4)(Si2O7)(OH)

Dollaseite-(Ce) - CaCeMg2AlSi3O11F(OH)

Vesuvianite (idocrase) - Ca10(Mg,Fe)2Al4(SiO4)5(Si2O7)2(OH)4

Cyclosilicates[edit]

Cyclosilicate specimens at the Museum of Geology, South Dakota

Main category: Cyclosilicates

Cyclosilicates (from Greek κύκλος kuklos, circle), or ring silicates, have linked tetrahedra with (TxO3x)2x− or a ratio of 1:3. These exist as 3-member (T3O9)6− and 6-member (T6O18)12− rings, where T stands for a tetrahedrally coordinated cation. Nickel-Strunz classification: 09.C

3-member ring

Benitoite - BaTi(Si3O9)

6-member ring

Axinite - (Ca,Fe,Mn)3Al2(BO3)(Si4O12)(OH)

Beryl/Emerald - Be3Al2(Si6O18)

Sugilite - KNa2(Fe,Mn,Al)2Li3Si12O30

Cordierite - (Mg,Fe)2Al3(Si5AlO18)

Tourmaline - (Na,Ca)(Al,Li,Mg)3-(Al,Fe,Mn)6(Si6O18(BO3)3(OH)4

Note that the ring in axinite contains two B and four Si tetrahedra and is highly distorted compared to the other 6-member ring cyclosilicates.

Inosilicates[edit]

Main category: Inosilicates

Inosilicates (from Greek ἴς is [genitive: ἰνός inos], fibre), or chain silicates, have interlocking chains of silicate tetrahedra with either SiO3, 1:3 ratio, for single chains or Si4O11, 4:11 ratio, for double chains. Nickel-Strunz classification: 09.D

Single chain inosilicates[edit]

Pyroxene group

Enstatite - orthoferrosilite series

Enstatite - MgSiO3

Ferrosilite - FeSiO3

Pigeonite - Ca0.25(Mg,Fe)1.75Si2O6

Diopside - hedenbergite series

Diopside - CaMgSi2O6

Hedenbergite - CaFeSi2O6

Augite - (Ca,Na)(Mg,Fe,Al)(Si,Al)2O6

Sodium pyroxene series

Jadeite - NaAlSi2O6

Aegirine (Acmite) - NaFe3+Si2O6

Spodumene - LiAlSi2O6

Pyroxenoid group

Wollastonite - CaSiO3

Rhodonite - MnSiO3

Pectolite - NaCa2(Si3O8)(OH)

Double chain inosilicates[edit]

Amphibole group

Anthophyllite - (Mg,Fe)7Si8O22(OH)2

Cumingtonite series

Cummingtonite - Fe2Mg5Si8O22(OH)2

Grunerite - Fe7Si8O22(OH)2

Tremolite series

Tremolite - Ca2Mg5Si8O22(OH)2

Actinolite - Ca2(Mg,Fe)5Si8O22(OH)2

Hornblende - (Ca,Na)2-3(Mg,Fe,Al)5Si6(Al,Si)2O22(OH)2

Sodium amphibole group

Glaucophane - Na2Mg3Al2Si8O22(OH)2

Riebeckite (asbestos) - Na2Fe2+3Fe3+2Si8O22(OH)2

Arfvedsonite - Na3(Fe,Mg)4FeSi8O22(OH)2

Phyllosilicates[edit]

Main category: Phyllosilicates

Phyllosilicates (from Greek φύλλον phyllon, leaf), or sheet silicates, form parallel sheets of silicate tetrahedra with Si2O5 or a 2:5 ratio. Nickel-Strunz classification: 09.E. All phyllosilicate minerals are hydrated, with either water or hydroxyl groups attached.

Kaolin

Serpentine group

Antigorite - Mg3Si2O5(OH)4

Chrysotile - Mg3Si2O5(OH)4

Lizardite - Mg3Si2O5(OH)4

Clay mineral group

Halloysite - Al2Si2O5(OH)4

Kaolinite - Al2Si2O5(OH)4

Illite - (K,H3O)(Al,Mg,Fe)2(Si,Al)4O10[(OH)2,(H2O)]

Montmorillonite - (Na,Ca)0.33(Al,Mg)2Si4O10(OH)2·nH2O

Vermiculite - (MgFe,Al)3(Al,Si)4O10(OH)2·4H2O

Talc - Mg3Si4O10(OH)2

Sepiolite - Mg4Si6O15(OH)2·6H2O

Palygorskite (or attapulgit)- (Mg,Al)2Si4O10(OH)·4(H2O)

Pyrophyllite - Al2Si4O10(OH)2

Mica group

Biotite - K(Mg,Fe)3(AlSi3)O10(OH)2

Muscovite - KAl2(AlSi3)O10(OH)2

Phlogopite - KMg3(AlSi3)O10(OH)2

Lepidolite - K(Li,Al)2-3(AlSi3)O10(OH)2

Margarite - CaAl2(Al2Si2)O10(OH)2

Glauconite - (K,Na)(Al,Mg,Fe)2(Si,Al)4O10(OH)2

Chlorite group

Chlorite - (Mg,Fe)3(Si,Al)4O10(OH)2•(Mg,Fe)3(OH)6

Tectosilicates[edit]

Main category: Tectosilicates

Tectosilicates, or "framework silicates," have a three-dimensional framework of silicate tetrahedra with SiO2 or a 1:2 ratio. This group comprises nearly 75% of the crust of the Earth. Tectosilicates, with the exception of the quartz group, are aluminosilicates. Nickel-Strunz classification: 09.F and 09.G, 04.DA (Quartz/ silica family)

Quartz

Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). Collected by Apollo 16 from the Lunar Highlands near Descartes Crater.

Quartz group

Quartz - SiO2

Tridymite - SiO2

Cristobalite - SiO2

Coesite - SiO2

Stishovite - SiO2

Feldspar family

Alkali-feldspars (potassium-feldspars)

Microcline - KAlSi3O8

Orthoclase - KAlSi3O8

Anorthoclase - (Na,K)AlSi3O8

Sanidine - KAlSi3O8

Albite - NaAlSi3O8

Plagioclase feldspars

Albite - NaAlSi3O8

Oligoclase - (Na,Ca)(Si,Al)4O8 (Na:Ca 4:1)

Andesine - (Na,Ca)(Si,Al)4O8 (Na:Ca 3:2)

Labradorite - (Na,Ca)(Si,Al)4O8 (Na:Ca 2:3)

Bytownite - (Na,Ca)(Si,Al)4O8 (Na:Ca 1:4)

Anorthite - CaAl2Si2O8

Feldspathoid family

Nosean - Na8Al6Si6O24(SO4)

Cancrinite - Na6Ca2(CO3,Al6Si6O24).2H2O

Leucite - KAlSi2O6

Nepheline - (Na,K)AlSiO4

Sodalite - Na8(AlSiO4)6Cl2

Hauyne - (Na,Ca)4-8Al6Si6(O,S)24(SO4,Cl)1-2

Lazurite - (Na,Ca)8(AlSiO4)6(SO4,S,Cl)2

Petalite - LiAlSi4O10

Scapolite group

Marialite - Na4(AlSi3O8)3(Cl2,CO3,SO4)

Meionite - Ca4(Al2Si2O8)3(Cl2CO3,SO4)

Analcime - NaAlSi2O6•H2O

Zeolite family

Natrolite - Na2Al2Si3O10•2H2O

Erionite - (Na2,K2,Ca)2Al4Si14O36·15H2O

Chabazite - CaAl2Si4O12•6H2O

Heulandite - CaAl2Si7O18•6H2O

Stilbite - NaCa2Al5Si13O36•17H2O

Scolecite - CaAl2Si3O10.3H2O

Mordenite - (Ca,Na2,K2)Al2Si10O24•7H2O

Recall quartz is made of silicon. Silicon is called the miracle element. It is shaped as a quadrant. Like carbon, which also has four valence electrons and is shaped as a quadrant, silicon is very important.

Fused quartz or fused silica is glass consisting of silica in amorphous (non-crystalline) form. It differs from traditional glasses in containing no other ingredients, which are typically added to glass to lower the melt temperature. Fused silica, therefore, has high working and melting temperatures. The optical and thermal properties of fused quartz are superior to those of other types of glass due to its purity. For these reasons, it finds use in situations such as semiconductor fabrication and laboratory equipment. It has better ultraviolet transmission than most other glasses, and so is used to make lenses and other optics for the ultraviolet spectrum. Its low coefficient of thermal expansion also makes it a useful material for precision mirror substrates.[1]

Feedstock[edit]

Fused quartz is produced by fusing (melting) high-purity silica sand, which consists of quartz crystals. Quartz contains only silicon and oxygen, although commercial quartz glass often contains impurities. The most dominant impurities are aluminium and titanium.[2]

Fusion[edit]

Melting is effected at approximately 2000 °C using either an electrically heated furnace (electrically fused) or a gas/oxygen-fuelled furnace (flame fused). Fused silica can be made from almost any silicon-rich chemical precursor, usually using a continuous process which involves flame oxidation of volatile silicon compounds to silicon dioxide, and thermal fusion of the resulting dust (although there are alternative processes). This results in a transparent glass with an ultra-high purity and improved optical transmission in the deep ultraviolet. One common method involves adding silicon tetrachloride to a hydrogen–oxygen flame, however use of this precursor results in environmentally unfriendly by-products including chlorine and hydrochloric acid. To eliminate these by-products, new processes have been developed using an alternative feedstock,[which?] which has also resulted in a higher purity fused silica with further improved deep ultraviolet transmission.[citation needed]

Product quality[edit]

Fused quartz is normally transparent, the process of fusion results in a material that is translucent. The material can however appear opaque owing to the presence small air bubbles trapped within the material. The water content (and therefore infrared transmission of fused quartz and fused silica) is determined by the manufacturing process. Flame fused material always has a higher water content due to the combination of the hydrocarbons and oxygen fuelling the furnace forming hydroxyl [OH] groups within the material. An IR grade material typically has an [OH] content of <10 parts per million.

Applications[edit]

Most of the applications of fused silica exploit its wide transparency range, which extends from the UV to the near IR. Fused silica is the key starting material for optical fiber, used for telecommunications.

Because of its strength and high melting point (compared to ordinary glass), fused silica is used as an envelope for halogen lamps and high-intensity discharge lamps, which must operate at a high envelope temperature to achieve their combination of high brightness and long life. Vacuum tubes with silica envelopes allowed for radiation-cooling by incandescent anodes.

Because of its strength fused silica was used in deep diving vessels such as the Bathysphere and Benthoscope.

The combination of strength, thermal stability, and UV transparency makes it an excellent substrate for projection masks for photolithography.

An EPROM with fused quartz window in the top of the package

Its UV transparency also finds uses in the semiconductor industry; an EPROM, or erasable programmable read only memory, is a type of memory chip that retains its data when its power supply is switched off, but which can be erased by exposure to strong ultraviolet light. EPROMs are recognizable by the transparent fused quartz window which sits on top of the package, through which the silicon chip is visible, and which permits exposure to UV light during erasing.

Due to the thermal stability and composition it is used in semiconductor fabrication furnaces.

Fused quartz has nearly ideal properties for fabricating first surface mirrors such as those used in telescopes. The material behaves in a predictable way and allows the optical fabricator to put a very smooth polish onto the surface and produce the desired figure with fewer testing iterations. In some instances, a high-purity UV grade of fused quartz has been used to make several of the individual uncoated lens elements of special purpose lenses including the Zeiss 105mm f/4.3 UV Sonnar, a lens formerly made for the Hasselblad camera, and the Nikon UV-Nikkor 105mm f/4.5 (presently sold[clarification needed] as the Nikon PF10545MF-UV) lens. These lenses are used for UV photography, as the quartz glass has a lower extinction rate than lens made with more common flint or crown glass formulas.

Fused quartz is also the material used for modern glass instruments such as the glass harp and the verrophone, and is also used for new builds of the historical glass harmonica. Here, the superior strength and structure of fused quartz gives it a greater dynamic range than the historically used lead crystal, and a clearer sound.

Refractory material applications[edit]

Fused silica as an industrial raw material is used to make various refractory shapes such as crucibles, trays, shrouds, and rollers for many high-temperature thermal processes including steelmaking, investment casting, and glass manufacture. Refractory shapes made from fused silica have excellent thermal shock resistance and are chemically inert to most elements and compounds including virtually all acids, regardless of concentration, except hydrofluoric acid which is very reactive even in fairly low concentrations. Translucent fused silica tubes are commonly used to sheathe electric elements in room heaters, industrial furnaces and other similar applications.

Owing to its low mechanical damping at ordinary temperatures, it is used for high-Q resonators, in particular, for wine-glass resonator of hemispherical resonator gyro (HRG).[3][4]

Quartz glassware is occasionally used in chemistry laboratories when standard borosilicate glass cannot withstand high temperatures; it is more commonly found as a very basic element, such as a tube in a furnace, or as a flask, the elements in direct exposure to the heat.

Physical properties[edit]

The extremely low coefficient of thermal expansion, about 5.5×10−7/°C (20–320 °C), accounts for its remarkable ability to undergo large, rapid temperature changes without cracking (see thermal shock).

Phosphorescence in fused quartz from an extremely intense pulse of ultraviolet light, centered at 170 nm, in a flashtube.

Fused quartz is prone to phosphorescence and "solarisation" (purplish discoloration) under intense UV illumination, as is often seen in flashtubes. "UV grade" synthetic fused silica (sold under various tradenames including "HPFS", "Spectrosil" and "Suprasil") has a very low metallic impurity content making it transparent deeper into the ultraviolet. An optic with a thickness of 1 cm will have a transmittance of about 50% at a wavelength of 170 nm, which drops to only a few percent at 160 nm. However, its infrared transmission is limited by strong water absorptions at 2.2 μm and 2.7 μm.

"Infrared grade" fused quartz (tradenames "Infrasil", "Vitreosil IR" and others) which is electrically fused, has a greater presence of metallic impurities, limiting its UV transmittance wavelength to around 250 nm, but a much lower water content, leading to excellent infrared transmission up to 3.6 μm wavelength. All grades of transparent fused quartz/fused silica have nearly identical physical properties.

The optical dispersion of fused silica can be approximated by the following Sellmeier equation:[5]

\varepsilon=n^2=1+\frac{0.6961663\lambda^2}{\lambda^2-0.0684043^2}+\frac{0.4079426\lambda^2}{\lambda^2-0.1162414^2}+\frac{0.8974794\lambda^2}{\lambda^2-9.896161^2},

where the wavelength \lambda is measured in micrometers. This equation is valid between 0.21 and 3.71 micrometers and at 20 °C.[5] Its validity was confirmed for wavelengths up to 6.7 µm.[6] Experimental data for the real (refractive index) and imaginary (absorption index) parts of the complex refractive index of fused quartz reported in the literature over the spectral range from 30 nm to 1000 µm has been reviewed by Kitamura et al.[6] and are available online.

QMRVycor is the brand name of Corning's high silica, high temperature glass. It provides very high thermal shock resistance. Vycor is approximately 96% silica and 4% boron trioxide, but unlike pure fused silica it can be readily manufactured in a variety of shapes

Vycor products are made by a multi-step process. First, a relatively soft alkali-borosilicate glass is melted and formed by typical glassworking techniques into the desired shape. This is heat-treated, which causes the material to separate into two intermingled "phases" with distinct chemical compositions. One phase is rich in alkali and boric oxide, and can be easily dissolved in acid. The other phase is mostly silica, which is insoluble. The glass object is then soaked in a hot acid solution, which leaches away the soluble glass phase, leaving an object which is mostly silica. At this stage, the glass is porous. Finally, the object is heated to more than 1200°C, which consolidates the porous structure, making the object shrink slightly and become non-porous. The finished material is classified as a "reconstructed glass".

For some applications the final step is skipped, leaving the glass porous. Such glass has a high affinity for water, and makes an excellent getter for water vapour. It is widely used in science and engineering.

Vycor has an extremely low coefficient of thermal expansion, just one quarter that of Pyrex.[1] This property makes the material suitable for use in applications which demand very-high-dimensional stability, such as metrology instruments, and for products that need to withstand high thermal shock loads.

Immersing the porous glass in certain chemical solutions before the final consolidation step produces a colored glass that can withstand high temperatures without degrading. This is used for colored glass filters for various applications.

Corning manufactures Vycor products for high-temperature applications, such as evaporating dishes.

Porous vycor is a prototypical matrix material for the study of confined liquid physics.

QMRShocked quartz

From Wikipedia, the free encyclopedia

Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. Under intense pressure (but limited temperature), the crystalline structure of quartz will be deformed along planes inside the crystal. These planes, which show up as lines under a microscope, are called planar deformation features (PDFs), or shock lamellae.

Discovery[edit]

Shocked quartz was discovered after underground nuclear bomb testing, which caused the intense pressures required to form shocked quartz. Eugene Shoemaker showed that shocked quartz is also found inside craters created by meteor impact, such as the Barringer Crater and Chicxulub crater.[1] The presence of shocked quartz proves that these craters were formed by an impact: a volcano would not generate the pressure required.

Prevalence[edit]

Shocked quartz is found worldwide, in the thin Cretaceous–Paleogene boundary layer, which occurs at the contact between Cretaceous and Paleogene rocks. This is further evidence (in addition to iridium enrichment) that the transition between the two geological periods was caused by a large impact. Though shocked quartz is only recently recognized, Eugene Shoemaker discovered it in building stones in the Bavarian town of Nördlingen.[2

Structure[edit]

Shocked quartz is associated with two high pressure polymorphs of silicon dioxide: coesite and stishovite. These polymorphs have a crystal structure different from standard quartz. Again, this structure can only be formed by intense pressure, but only moderate temperatures. High temperatures would anneal the quartz back to its standard form. Coesite and stishovite are also indicative of impact (or nuclear explosion).

QMRHydrothermal breccia in the Cloghleagh Iron Mine, near Blessington in Ireland, composed mainly of quartz and manganese oxides, the result of seismic activity about 12 million years ago

QMRLechatelierite

From Wikipedia, the free encyclopedia

Lechatelierite created by high voltage power line arcing on rocky soil.

Lechatelierite is silica glass, amorphous SiO2. One common way in which lechatelierite forms naturally is by very high temperature melting of quartz sand during a lightning strike. The result is an irregular, branching, often foamy hollow tube of silica glass called a fulgurite.[1]

Lechatelierite also forms as the result of high pressure shock metamorphism during meteorite impact cratering and is a common component of a type of glassy ejecta called tektites. Most tektites are blobs of impure glassy material, but tektites from the Sahara Desert in Libya and Egypt, known as Libyan desert glass, are composed of almost pure silica, that is almost pure lechatelierite.[2] High pressure experiments have shown that shock pressures of 85 GPa are needed to produce lechatelierite in quartz grains embedded in granite.[3]

Lechatelierite was formed during the impact of a meteorite into a layer of Coconino Sandstone at Meteor Crater in Arizona. During the rapid pressure reduction following the impact, steam expanded the newly formed lechatelierite. The shattered and expanded glass has a density less than that of water.[4]

Lechatelierite may also form artificially, a unique example being the trinitite produced by melting of quartz sand at the first nuclear bomb explosion at Trinity Flats, White Sands, New Mexico.[5]

Lechatelierite is a mineraloid as it does not have a crystal structure. Although not a true mineral, it is often classified in the quartz mineral group.

QMRThe term "granitic" means granite-like and is applied to granite and a group of intrusive igneous rocks with similar textures and slight variations in composition and origin. These rocks mainly consist of feldspar, quartz, mica, and amphibole minerals, which form an interlocking, somewhat equigranular matrix of feldspar and quartz with scattered darker biotite mica and amphibole (often hornblende) peppering the lighter color minerals. Occasionally some individual crystals (phenocrysts) are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic texture is known as a granite porphyry. Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks. Petrographic examination is required for identification of specific types of granitoids.[1]

SiO2 72.04% (silica)

Al2O3 14.42% (alumina)

K2O 4.12%

Na2O 3.69%

CaO 1.82%

FeO 1.68%

Fe2O3 1.22%

MgO 0.71%

TiO2 0.30%

P2O5 0.12%

MnO 0.05%

Granitoids are a ubiquitous component of the crust. They have crystallized from magmas that have compositions at or near a eutectic point (or a temperature minimum on a cotectic curve). Magmas will evolve to the eutectic because of igneous differentiation, or because they represent low degrees of partial melting. Fractional crystallisation serves to reduce a melt in iron, magnesium, titanium, calcium and sodium, and enrich the melt in potassium and silicon – alkali feldspar (rich in potassium) and quartz (SiO2), are two of the defining constituents of granite.

This process operates regardless of the origin of the parental magma to the granite, and regardless of its chemistry. However, the composition and origin of the magma that differentiates into granite leaves certain geochemical and mineral evidence as to what the granite's parental rock was. The final mineralogy, texture and chemical composition of a granite is often distinctive as to its origin. For instance, a granite that is formed from melted sediments may have more alkali feldspar, whereas a granite derived from melted basalt may be richer in plagioclase feldspar. It is on this basis that the modern "alphabet" classification schemes are based. Granite has a slow cooling process which forms larger crystals.

QMRA QAPF diagram is a double triangle diagram which is used to classify igneous rocks based on mineralogic composition. The acronym, QAPF, stands for "Quartz, Alkali feldspar, Plagioclase, Feldspathoid (Foid)". These are the mineral groups used for classification in QAPF diagram. Q, A, P and F percentages are normalized (recalculated so that their sum is 100%).

QMRMagma is a complex high-temperature fluid substance. Temperatures of most magmas are in the range 700 °C to 1300 °C (or 1300 °F to 2400 °F), but very rare carbonatite magmas may be as cool as 600 °C, and komatiite magmas may have been as hot as 1600 °C. Most magmas are silicate mixtures.[2]

Characteristics of the four different magma types are as follows:

Ultramafic (picritic)

SiO2 < 45%

Fe–Mg > 8% up to 32%MgO

Temperature: up to 1500°C

Viscosity: Very Low

Eruptive behavior: gentle or very explosive (kimberilites)

Distribution: divergent plate boundaries, hot spots, convergent plate boundaries; komatiite and other ultramafic lavas are mostly Archean and were formed from a higher geothermal gradient and are unknown in the present

Mafic (basaltic)

SiO2 < 50%

FeO and MgO typically < 10 wt%

Temperature: up to ~1300°C

Viscosity: Low

Eruptive behavior: gentle

Distribution: divergent plate boundaries, hot spots, convergent plate boundaries

Intermediate (andesitic)

SiO2 ~ 60%

Fe–Mg: ~ 3%th

Temperature: ~1000°C

Viscosity: Intermediate

Eruptive behavior: explosive or effusive

Distribution: convergent plate boundaries, island arcs

Felsic (rhyolitic)

SiO2 > 70%

Fe–Mg: ~ 2%

Temp: < 900°C

Viscosity: High

Eruptive behavior: explosive or effusive

Distribution: common in hot spots in continental crust (Yellowstone National Park) and in continental rifts

Composition, melt structure and properties[edit]

Silicate melts are composed mainly of silicon, oxygen, aluminium, alkalis (sodium, potassium, calcium), magnesium and iron. Silicon atoms are in tetrahedral coordination with oxygen, as in almost all silicate minerals, but in melts atomic order is preserved only over short distances. The physical behaviours of melts depend upon their atomic structures as well as upon temperature and pressure and composition.[8]

Viscosity is a key melt property in understanding the behaviour of magmas. More silica-rich melts are typically more polymerized, with more linkage of silica tetrahedra, and so are more viscous. Dissolution of water drastically reduces melt viscosity. Higher-temperature melts are less viscous.

Generally speaking, more mafic magmas, such as those that form basalt, are hotter and less viscous than more silica-rich magmas, such as those that form rhyolite. Low viscosity leads to gentler, less explosive eruptions.

Rock types produced by small degrees of partial melting in the Earth's mantle are typically alkaline (Ca, Na), potassic (K) and/or peralkaline (high aluminium to silica ratio). Typically, primitive melts of this composition form lamprophyre, lamproite, kimberlite and sometimes nepheline-bearing mafic rocks such as alkali basalts and essexite gabbros or even carbonatite.

Composition[edit]

It is usually very difficult to change the bulk composition of a large mass of rock, so composition is the basic control on whether a rock will melt at any given temperature and pressure. The composition of a rock may also be considered to include volatile phases such as water and carbon dioxide.

The presence of volatile phases in a rock under pressure can stabilize a melt fraction. The presence of even 0.8% water may reduce the temperature of melting by as much as 100 °C. Conversely, the loss of water and volatiles from a magma may cause it to essentially freeze or solidify.

Also a major portion of all magma is silica, which is a compound of silicon and oxygen. Magma also contains gases, which expand as the magma rises. Magma that is high in silica resists flowing, so expanding gases are trapped in it. Pressure builds up until the gases blast out in a violent, dangerous explosion. Magma that is relatively poor in silica flows easily, so gas bubbles move up through it and escape fairly gently.

Again silicon has four valence electrons and thus reflects the cross/quadrant.

QMRIn petrology the mineral clinopyroxene is used for temperature and pressure calculations of the magma that produced igneous rock containing this mineral. Clinopyroxene thermobarometry is one of several geothermobarometers. Two things makes this method especially useful: first, clinopyroxene is a common phenocryst in igneous rocks and easy to identify; second, the crystallization of the jadeite component of clinopyroxene implies a growth in molar volume being thus a good indicator of pressure.

The minerals and liquids involved in clinopyroxene thermobarometry are these four:

Augite - (Ca,Mg,Fe)SiO3

Diopside - MgCaSi2O6

Hedenbergite - CaFeSi2O6

Jadeite - Na(Al,Fe3+)Si2O6

Phenocryst

From Wikipedia, the free encyclopedia

Granites often have large feldspathic phenocrysts. This granite, from the Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coin (diameter 2.3 cm) for scale.

A phenocryst is a relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock. Such rocks that have a distinct difference in the size of the crystals are called porphyries, and the adjective porphyritic is used to describe them. Phenocrysts often have euhedral forms, either due to early growth within a magma, or by post-emplacement recrystallization. Normally the term phenocryst is not used unless the crystals are directly observable, which is sometimes stated as greater than .5 millimeter in diameter.[1] Phenocrysts below this level, but still larger than the groundmass crystals, are termed microphenocrysts. Very large phenocrysts are termed megaphenocrysts. Some rocks contain both microphenocrysts and megaphenocrysts.[2] In metamorphic rocks, crystals similar to phenocrysts are called porphyroblasts.

Phenocrysts are more often found in the lighter (higher silica) igneous rocks such as felsites and andesites, although they occur throughout the igneous spectrum including in the ultramafics. The largest crystals found in some pegmatites are often phenocrysts being significantly larger than the other minerals.

Analysis using phenocrysts[edit]

Geologists use phenocrysts to help determine rock origins and transformations, as when and whether crystals form depends on pressure and on temperature. Fumiko Shido first applied this technique to oceanic basalts,[8] further development came from Tsugio Shibata,[9] and from W. B. Bryan.[10]

Other characteristics[edit]

Plagioclase phenocrysts often exhibit zoning with a more calcic core surrounded by progressively more sodic rinds. This zoning reflects the change in magma composition as crystallization progresses.[11] In rapakivi granites, phenocrysts of orthoclase are enveloped within rinds of sodic plagioclase such as oligoclase. In shallow intrusives or volcanic flows phenocrysts which formed before eruption or shallow emplacement are surrounded by a fine-grained to glassy matrix. These volcanic phenocrysts often show flow banding, a parallel arrangement of lath-shaped crystals. These characteristics provide clues to the rocks' origins. Similarly, intragranular microfractures and any intergrowth among crystals provide additional clues.[12]

QMRUltramafic (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed of usually greater than 90% mafic minerals (dark colored, high magnesium and iron content). The Earth's mantle is composed of ultramafic rocks. Ultrabasic is a more inclusive term that includes igneous rocks with low silica content that may not be extremely enriched in Fe and Mg, such as carbonatites and ultrapotassic igneous rocks.

QMRSilurian[edit]

Main article: Silurian

The Silurian spans from 440 million years to 415 million years ago. The Silurian saw the healing of the earth that recovered from the Snowball Earth. This period saw the mass evolution of fish, as jaw-less fish became more numerous, jawed fish evolved, and the first freshwater fish evolved, though arthropods, such as sea scorpions, were still apex predators. Fully terrestrial life evolved, which included early arachnids, fungi, and centipedes. Also, the evolution of vascular plants (Cooksonia) allowed plants to gain a foothold on land. These early terrestrial plants are the forerunners of all plant life on land. During this time, there are four continents: Gondwana (Africa, South America, Australia, Antarctica, India), Laurentia (North America with parts of Europe), Baltica (the rest of Europe), and Siberia (Northern Asia). The recent rise in sea levels provided many new species to thrive in water.[

QMRCoquina, a rock composed of clasts of broken shells, can only form in energetic water. The form of a clast can be described by using four parameters:[14][15]

Surface texture describes the amount of small-scale relief of the surface of a grain that is too small to influence the general shape.

rounding describes the general smoothness of the shape of a grain.

'Sphericity' describes the degree to which the grain approaches a sphere.

'Grain form' describes the three dimensional shape of the grain.

QMRThe chain silicate structure of the pyroxenes offers much flexibility in the incorporation of various cations and the names of the pyroxene minerals are primarily defined by their chemical composition. Pyroxene minerals are named according to the chemical species occupying the X (or M2) site, the Y (or M1) site, and the tetrahedral T site. Cations in Y (M1) site are closely bound to 6 oxygens in octahedral coordination. Cations in the X (M2) site can be coordinated with 6 to 8 oxygen atoms, depending on the cation size. Twenty mineral names are recognised by the International Mineralogical Association's Commission on New Minerals and Mineral Names and 105 previously used names have been discarded (Morimoto et al., 1989).

A typical pyroxene has mostly silicon in the tetrahedral site and predominately ions with a charge of +2 in both the X and Y sites, giving the approximate formula XYT2O6. The names of the common calcium – iron – magnesium pyroxenes are defined in the 'pyroxene quadrilateral' shown in Figure 2. The enstatite-ferrosilite series ([Mg,Fe]SiO3) contain up to 5 mol.% calcium and exists in three polymorphs, orthorhombic orthoenstatite and protoenstatite and monoclinic clinoenstatite (and the ferrosilite equivalents). Increasing the calcium content prevents the formation of the orthorhombic phases and pigeonite ([Mg,Fe,Ca][Mg,Fe]Si2O6) only crystallises in the monoclinic system. There is not complete solid solution in calcium content and Mg-Fe-Ca pyroxenes with calcium contents between about 15 and 25 mol.% are not stable with respect to a pair of exolved crystals. This leads to a miscibility gap between pigeonite and augite compositions. There is an arbitrary separation between augite and the diopside-hedenbergite (CaMgSi2O6 – CaFeSi2O6) solid solution. The divide is taken at >45 mol.% Ca. As the calcium ion cannot occupy the Y site, pyroxenes with more than 50 mol.% calcium are not possible. A related mineral wollastonite has the formula of the hypothetical calcium end member but important structural differences mean that it is not grouped with the pyroxenes.

Figure 3: The nomenclature of the sodium pyroxenes.

Magnesium, calcium and iron are by no means the only cations that can occupy the X and Y sites in the pyroxene structure. A second important series of pyroxene minerals are the sodium-rich pyroxenes, corresponding to nomenclature shown in Figure 3. The inclusion of sodium, which has a charge of +1, into the pyroxene implies the need for a mechanism to make up the "missing" positive charge. In jadeite and aegirine this is added by the inclusion of a +3 cation (aluminium and iron(III) respectively) on the Y site. Sodium pyroxenes with more than 20 mol.% calcium, magnesium or iron(II) components are known as omphacite and aegirine-augite, with 80% or more of these components the pyroxene falls in the quadrilateral shown in figure 2.

Table 1 shows the wide range of other cations that can be accommodated in the pyroxene structure, and indicates the sites that they occupy.

Table 1: Order of cation occupation in the pyroxenes

T Si Al Fe3+

Y Al Fe3+ Ti4+ Cr V Ti3+ Zr Sc Zn Mg Fe2+ Mn

X Mg Fe2+ Mn Li Ca Na

In assigning ions to sites the basic rule is to work from left to right in this table first assigning all silicon to the T site then filling the site with remaining aluminium and finally iron(III), extra aluminium or iron can be accommodated in the Y site and bulkier ions on the X site. Not all the resulting mechanisms to achieve charge neutrality follow the sodium example above and there are several alternative schemes:

Coupled substitutions of 1+ and 3+ ions on the X and Y sites respectively. For example, Na and Al give the jadeite (NaAlSi2O6) composition.

Coupled substitution of a 1+ ion on the X site and a mixture of equal numbers of 2+ and 4+ ions on the Y site. This leads to e.g. NaFe2+0.5Ti4+0.5Si2O6.

The Tschermak substitution where a 3+ ion occupies the Y site and a T site leading to e.g. CaAlAlSiO6.

In nature, more than one substitution may be found in the same mineral.

QMRThe mica group of sheet silicate (phyllosilicate) minerals includes several closely related materials having nearly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition. The nearly perfect cleavage, which is the most prominent characteristic of mica, is explained by the hexagonal sheet-like arrangement of its atoms.

The word mica is derived from the Latin word mica, meaning a crumb, and probably influenced by micare, to glitter.[5]

Trioctahedral micas[edit]

Common micas:

Biotite

Lepidolite

Muscovite

Phlogopite

Zinnwaldite

Brittle micas:

Clintonite

Interlayer deficient micas[edit]

Very fine-grained micas, which typically show more variation in ion and water content, are informally termed "clay micas". They include:

Hydro-muscovite with H3O+ along with K in the X site;

Illite with a K deficiency in the X site and correspondingly more Si in the Z site;

Phengite with Mg or Fe2+ substituting for Al in the Y site and a corresponding increase in Si in the Z site.

Occurrence and production[edit]

File:Mica.webm

Mica embedded in metamorphic rock

Mica is widely distributed and occurs in igneous, metamorphic and sedimentary regimes. Large crystals of mica used for various applications are typically mined from granitic pegmatites.

Until the 19th century, large crystals of mica were quite rare and expensive as a result of the limited supply in Europe. However, their price dramatically dropped when large reserves were found and mined in Africa and South America during the early 19th century. The largest documented single crystal of mica (phlogopite) was found in Lacey Mine, Ontario, Canada; it measured 10 × 4.3 × 4.3 m and weighed about 330 tonnes.[7] Similar-sized crystals were also found in Karelia, Russia.[8]

The British Geological Survey reported that as of 2005, Koderma district in Jharkhand state in India had the largest deposits of mica in the world. China was the top producer of mica with almost a third of the global share, closely followed by the US, South Korea and Canada. Large deposits of sheet mica were mined in New England from the 19th century to the 1970s. Large mines existed in Connecticut, New Hampshire, and Maine.

Scrap and flake mica is produced all over the world. In 2010, the major producers were Russia (100,000 tonnes), Finland (68,000 t), United States (53,000 t), South Korea (50,000 t), France (20,000 t) and Canada (15,000 t). The total production was 350,000 t, although no reliable data were available for China. Most sheet mica was produced in India (3,500 t) and Russia (1,500 t).[9] Flake mica comes from several sources: the metamorphic rock called schist as a byproduct of processing feldspar and kaolin resources, from placer deposits, and from pegmatites. Sheet mica is considerably less abundant than flake and scrap mica, and is occasionally recovered from mining scrap and flake mica. The most important sources of sheet mica are pegmatite deposits. Sheet mica prices vary with grade and can range from less than $1 per kilogram for low-quality mica to more than $2,000 per kilogram for the highest quality.

Pyroxene minerals[edit]

First X-ray diffraction view of Martian soil - CheMin analysis reveals feldspar, pyroxenes, olivine and more (Curiosity rover at "Rocknest", October 17, 2012).[1]

Clinopyroxenes (monoclinic; abbreviated CPx)

Aegirine (Sodium Iron Silicate)

Augite (Calcium Sodium Magnesium Iron Aluminium Silicate)

Clinoenstatite (Magnesium Silicate)

Diopside (Calcium Magnesium Silicate, CaMgSi2O6)

Esseneite (Calcium Iron Aluminium Silicate)

Hedenbergite (Calcium Iron Silicate)

Jadeite (Sodium Aluminium Silicate)

Jervisite (Sodium Calcium Iron Scandium Magnesium Silicate)

Johannsenite (Calcium Manganese Silicate)

Kanoite (Manganese Magnesium Silicate)

Kosmochlor (Sodium Chromium Silicate)

Namansilite (Sodium Manganese Silicate)

Natalyite (Sodium Vanadium Chromium Silicate)

Omphacite (Calcium Sodium Magnesium Iron Aluminium Silicate)

Petedunnite (Calcium Zinc Manganese Iron Magnesium Silicate)

Pigeonite (Calcium Magnesium Iron Silicate)

Spodumene (Lithium Aluminium Silicate)

Orthopyroxenes (orthorhombic; abbreviated OPx)

Hypersthene (Magnesium Iron Silicate)

Donpeacorite, (MgMn)MgSi2O6

Enstatite, Mg2Si2O6

Ferrosilite, Fe2Si2O6

Nchwaningite (Hydrated Manganese Silicate)

QMRGenetic classification[edit]

Based on the processes responsible for their formation, sedimentary rocks can be subdivided into four groups: clastic sedimentary rocks, biochemical (or biogenic) sedimentary rocks, chemical sedimentary rocks and a fourth category for "other" sedimentary rocks formed by impacts, volcanism, and other minor processes.

Clastic sedimentary rocks[edit]

Main article: Clastic rock

Claystone deposited in Glacial Lake Missoula, Montana, United States. Note the very fine and flat bedding, common for distal lacustrine deposition.

Clastic sedimentary rocks are composed of silicate minerals and rock fragments that were transported by moving fluids (as bed load, suspended load, or by sediment gravity flows) and were deposited when these fluids came to rest. Clastic rocks are composed largely of quartz, feldspar, rock (lithic) fragments, clay minerals, and mica; numerous other minerals may be present as accessories and may be important locally.

Clastic sediment, and thus clastic sedimentary rocks, are subdivided according to the dominant particle size (diameter). Most geologists use the Udden-Wentworth grain size scale and divide unconsolidated sediment into three fractions: gravel (>2 mm diameter), sand (1/16 to 2 mm diameter), and mud (clay is <1/256 mm and silt is between 1/16 and 1/256 mm). The classification of clastic sedimentary rocks parallels this scheme; conglomerates and breccias are made mostly of gravel, sandstones are made mostly of sand, and mudrocks are made mostly of mud. This tripartite subdivision is mirrored by the broad categories of rudites, arenites, and lutites, respectively, in older literature.

Subdivision of these three broad categories is based on differences in clast shape (conglomerates and breccias), composition (sandstones), grain size and/or texture (mudrocks).

Conglomerates and breccias[edit]

Conglomerates are dominantly composed of rounded gravel and breccias are composed of dominantly angular gravel.

Sandstones[edit]

Sedimentary rock with sandstone in Malta

Sandstone classification schemes vary widely, but most geologists have adopted the Dott scheme,[2] which uses the relative abundance of quartz, feldspar, and lithic framework grains and the abundance of muddy matrix between these larger grains.

Composition of framework grains

The relative abundance of sand-sized framework grains determines the first word in a sandstone name. For naming purposes, the abundance of framework grains is normalized to quartz, feldspar, and lithic fragments formed from other rocks. These are the three most abundant components of sandstones; all other minerals are considered accessories and not used in the naming of the rock, regardless of abundance.

Quartz sandstones have >90% quartz grains

Feldspathic sandstones have <90% quartz grains and more feldspar grains than lithic grains

Lithic sandstones have <90% quartz grains and more lithic grains than feldspar grains

Abundance of muddy matrix between sand grains

When sand-sized particles are deposited, the space between the sand grains either remains open or is filled with mud (silt and/or clay sized particle).

"Clean" sandstones with open pore space (that may later be filled with cement) are called arenites.

Muddy sandstones with abundant (>10%) muddy matrix are called wackes.

Six sandstone names are possible using descriptors for grain composition (quartz-, feldspathic-, and lithic-) and amount of matrix (wacke or arenite). For example, a quartz arenite would be composed of mostly (>90%) quartz grains and have little/no clayey matrix between the grains, a lithic wacke would have abundant lithic grains (<90% quartz, remainder would have more lithics than feldspar) and abundant muddy matrix, etc.

Although the Dott classification scheme[2] is widely used by sedimentologists, common names like greywacke, arkose, and quartz sandstone are still widely used by nonspecialists and in popular literature.

Mudrocks[edit]

Lower Antelope Canyon was carved out of the surrounding sandstone by both mechanical weathering and chemical weathering. Wind, sand, and water from flash flooding are the primary weathering agents.

Mudrocks are sedimentary rocks composed of at least 50% silt- and clay-sized particles. These relatively fine-grained particles are commonly transported as suspended particles by turbulent flow in water or air, and deposited as the flow calms and the particles settle out of suspension.

Most authors presently use the term "mudrock" to refer to all rocks composed dominantly of mud.[3][4][5][6] Mudrocks can be divided into siltstones (composed dominantly of silt-sized particles), mudstones (subequal mixture of silt- and clay-sized particles), and claystones (composed mostly of clay-sized particles).[3][4] Most authors use "shale" as a term for a fissile mudrock (regardless of grain size) although some older literature uses the term "shale" as a synonym for mudrock.

Biochemical sedimentary rocks[edit]

Outcrop of Ordovician oil shale (kukersite), northern Estonia

Biochemical sedimentary rocks are created when organisms use materials dissolved in air or water to build their tissue. Examples include:

Most types of limestone are formed from the calcareous skeletons of organisms such as corals, mollusks, and foraminifera.

Coal, formed from plants that have removed carbon from the atmosphere and combined it with other elements to build their tissue.

Deposits of chert formed from the accumulation of siliceous skeletons from microscopic organisms such as radiolaria and diatoms.

Chemical sedimentary rocks[edit]

Chemical sedimentary rock forms when mineral constituents in solution become supersaturated and inorganically precipitate. Common chemical sedimentary rocks include oolitic limestone and rocks composed of evaporite minerals, such as halite (rock salt), sylvite, barite and gypsum.

"Other" sedimentary rocks[edit]

This fourth miscellaneous category includes rocks formed by Pyroclastic flows, impact breccias, volcanic breccias, and other relatively uncommon processes.

QMR Mold materials[edit]

There are four main components for making a sand casting mold: base sand, a binder, additives, and a parting compound.

Again sand is made up of silicon, called the miracle element. It has four valence electrons and resembles a quadrant.

Silica sand[edit]

Silica (SiO2) sand is the sand found on a beach and is also the most commonly used sand. It is made by either crushing sandstone or taken from natural occurring locations, such as beaches and river beds. The fusion point of pure silica is 1,760 °C (3,200 °F), however the sands used have a lower melting point due to impurities. For high melting point casting, such as steels, a minimum of 98% pure silica sand must be used; however for lower melting point metals, such as cast iron and non-ferrous metals, a lower purity sand can be used (between 94 and 98% pure).[11]

Silica sand is the most commonly used sand because of its great abundance, and, thus, low cost (therein being its greatest advantage). Its disadvantages are high thermal expansion, which can cause casting defects with high melting point metals, and low thermal conductivity, which can lead to unsound casting. It also cannot be used with certain basic metal because it will chemically interact with the metal forming surface defect. Finally, it causes silicosis in foundry workers.[14]

Olivine sand[edit]

Olivine is a mixture of orthosilicates of iron and magnesium from the mineral dunite. Its main advantage is that it is free from silica, therefore it can be used with basic metals, such as manganese steels. Other advantages include a low thermal expansion, high thermal conductivity, and high fusion point. Finally, it is safer to use than silica, therefore it is popular in Europe.[14]

Chromite sand[edit]

Chromite sand is a solid solution of spinels. Its advantages are a low percentage of silica, a very high fusion point (1,850 °C (3,360 °F)), and a very high thermal conductivity. Its disadvantage is its costliness, therefore it's only used with expensive alloy steel casting and to make cores.[14]

Zircon sand[edit]

Zircon sand is a compound of approximately two-thirds zircon oxide (Zr2O) and one-third silica. It has the highest fusion point of all the base sands at 2,600 °C (4,710 °F), a very low thermal expansion, and a high thermal conductivity. Because of these good properties it is commonly used when casting alloy steels and other expensive alloys. It is also used as a mold wash (a coating applied to the molding cavity) to improve surface finish. However, it is expensive and not readily available.[14]

Chamotte sand[edit]

Chamotte is made by calcining fire clay (Al2O3-SiO2) above 1,100 °C (2,010 °F). Its fusion point is 1,750 °C (3,180 °F) and has low thermal expansion. It is the second cheapest sand, however it is still twice as expensive as silica. Its disadvantages are very coarse grains, which result in a poor surface finish, and it is limited to dry sand molding. Mold washes are used to overcome the surface finish problem. This sand is usually used when casting large steel workpieces.[14][15]

QMRSilicon carbide (SiC), also known as carborundum /kɑrbəˈrʌndəm/, is a compound of silicon and carbon with chemical formula SiC. It occurs in nature as the extremely rare mineral moissanite. Silicon carbide powder has been mass-produced since 1893 for use as an abrasive. Grains of silicon carbide can be bonded together by sintering to form very hard ceramics that are widely used in applications requiring high endurance, such as car brakes, car clutches and ceramic plates in bulletproof vests. Electronic applications of silicon carbide as light-emitting diodes (LEDs) and detectors in early radios were first demonstrated around 1907. SiC is used in semiconductor electronics devices that operate at high temperatures or high voltages or both. Large single crystals of silicon carbide can be grown by the Lely method; they can be cut into gems known as synthetic moissanite. Silicon carbide with high surface area can be produced from SiO2 contained in plant material.

Early experiments[edit]

Non-systematic, less-recognized, and often unverified syntheses of silicon carbide include

J. J. Berzelius's reduction of potassium fluorosilicate by potassium (1810)

César-Mansuète Despretz's passing an electric current through a carbon rod embedded in sand (1849)

Robert Sydney Marsden's dissolution of silica in molten silver in a graphite crucible (1881)

Paul Schuetzenberger's heating of a mixture of silicon and silica in a graphite crucible (1881)

Albert Colson's heating of silicon under a stream of ethylene (1882).[4]

Wide-scale production[edit]

A replication of H. J. Round's LED experiments

Wide-scale production is credited to Edward Goodrich Acheson in 1890.[5] Acheson was attempting to prepare artificial diamonds when he heated a mixture of clay (aluminum silicate) and powdered coke (fuel) (carbon) in an iron bowl. He called the blue crystals that formed Carborundum, believing it to be a new compound of carbon and aluminum, similar to corundum. In 1893, Henri Moissan discovered the very rare naturally-occurring SiC mineral while examining rock samples found in the Canyon Diablo meteorite in Arizona. The mineral was named moissanite in his honor. Moissan also synthesized SiC by several routes, including dissolution of carbon in molten silicon, melting a mixture of calcium carbide and silica, and by reducing silica with carbon in an electric furnace.

Acheson patented the method for making silicon carbide powder on February 28, 1893.[6] Acheson also developed the electric batch furnace by which SiC is still made today and formed the Carborundum Company to manufacture bulk SiC, initially for use as an abrasive.[7] In 1900 the company settled with the Electric Smelting and Aluminum Company when a judge's decision gave "priority broadly" to its founders "for reducing ores and other substances by the incandescent method".[8] It is said that Acheson was trying to dissolve carbon in molten corundum (alumina) and discovered the presence of hard, blue-black crystals which he believed to be a compound of carbon and corundum: hence carborundum. It may be that he named the material "carborundum" by analogy to corundum, which is another very hard substance (9 on the Mohs scale).

The first use of SiC was as an abrasive. This was followed by electronic applications. In the beginning of the 20th century, silicon carbide was used as a detector in the first radios.[9] In 1907 Henry Joseph Round produced the first LED by applying a voltage to a SiC crystal and observing yellow, green and orange emission at the cathode. Those experiments were later repeated by O. V. Losev in the Soviet Union in 1923.[10]

Natural occurrence[edit]

Moissanite single crystal (≈1 mm in size)

Naturally occurring moissanite is found in only minute quantities in certain types of meteorite and in corundum deposits and kimberlite. Virtually all the silicon carbide sold in the world, including moissanite jewels, is synthetic. Natural moissanite was first found in 1893 as a small component of the Canyon Diablo meteorite in Arizona by Dr. Ferdinand Henri Moissan, after whom the material was named in 1905.[11] Moissan's discovery of naturally occurring SiC was initially disputed because his sample may have been contaminated by silicon carbide saw blades that were already on the market at that time.[12]

While rare on Earth, silicon carbide is remarkably common in space. It is a common form of stardust found around carbon-rich stars, and examples of this stardust have been found in pristine condition in primitive (unaltered) meteorites. The silicon carbide found in space and in meteorites is almost exclusively the beta-polymorph. Analysis of SiC grains found in the Murchison meteorite, a carbonaceous chondrite meteorite, has revealed anomalous isotopic ratios of carbon and silicon, indicating an origin from outside the solar system; 99% of these SiC grains originate around carbon-rich asymptotic giant branch stars.[13] SiC is commonly found around these stars as deduced from their infrared spectra.[14]

Production[edit]

Because of the rarity of natural moissanite, most silicon carbide is synthetic. It is used as an abrasive, and more recently as a semiconductor and diamond simulant of gem quality. The simplest manufacturing process is to combine silica sand and carbon in an Acheson graphite electric resistance furnace at a high temperature, between 1,600 °C (2,910 °F) and 2,500 °C (4,530 °F). Fine SiO2 particles in plant material (e.g. rice husks) can be converted to SiC by heating in the excess carbon from the organic material.[15] The silica fume, which is a byproduct of producing silicon metal and ferrosilicon alloys, also can be converted to SiC by heating with graphite at 1,500 °C (2,730 °F).[16]

Synthetic SiC crystals ~3 mm in diameter

Synthetic SiC Lely crystals

The material formed in the Acheson furnace varies in purity, according to its distance from the graphite resistor heat source. Colorless, pale yellow and green crystals have the highest purity and are found closest to the resistor. The color changes to blue and black at greater distance from the resistor, and these darker crystals are less pure. Nitrogen and aluminium are common impurities, and they affect the electrical conductivity of SiC.[17]

Pure silicon carbide can be made by the so-called Lely process,[18] in which SiC powder is sublimated into high-temperature species of silicon, carbon, silicon dicarbide (SiC2), and disilicon carbide (Si2C) in an argon gas ambient at 2500 °C and redeposited into flake-like single crystals,[19] sized up to 2×2 cm, at a slightly colder substrate. This process yields high-quality single crystals, mostly of 6H-SiC phase (because of high growth temperature). A modified Lely process involving induction heating in graphite crucibles yields even larger single crystals of 4 inches (10 cm) in diameter, having a section 81 times larger compared to the conventional Lely process.[20] Cubic SiC is usually grown by the more expensive process of chemical vapor deposition (CVD).[17][21] Homoepitaxial and heteroepitaxial SiC layers can be grown employing both gas and liquid phase approaches.[22] Pure silicon carbide can also be prepared by the thermal decomposition of a polymer, poly(methylsilyne), under an inert atmosphere at low temperatures. Relative to the CVD process, the pyrolysis method is advantageous because the polymer can be formed into various shapes prior to thermalization into the ceramic.[23][24][25][26]

Production[edit]

Synthetic SiC crystals ~3 mm in diameter

Synthetic SiC Lely crystals

Silicon carbide exists in about 250 crystalline forms.[27] The polymorphism of SiC is characterized by a large family of similar crystalline structures called polytypes. They are variations of the same chemical compound that are identical in two dimensions and differ in the third. Thus, they can be viewed as layers stacked in a certain sequence.[28]

Alpha silicon carbide (α-SiC) is the most commonly encountered polymorph; it is formed at temperatures greater than 1700 °C and has a hexagonal crystal structure (similar to Wurtzite). The beta modification (β-SiC), with a zinc blende crystal structure (similar to diamond), is formed at temperatures below 1700 °C.[29] Until recently, the beta form has had relatively few commercial uses, although there is now increasing interest in its use as a support for heterogeneous catalysts, owing to its higher surface area compared to the alpha form.

Properties of major SiC polytypes[3][23]

Polytype 3C (β) 4H 6H (α)

Crystal structure Zinc blende (cubic) Hexagonal Hexagonal

Space group T2d-F43m C46v-P63mc C46v-P63mc

Pearson symbol cF8 hP8 hP12

Lattice constants (Å) 4.3596 3.0730; 10.053 3.0810; 15.12

Density (g/cm3) 3.21 3.21 3.21

Bandgap (eV) 2.36 3.23 3.05

Bulk modulus (GPa) 250 220 220

Thermal conductivity (W cm−1K−1)

@ 300K (see [30] for temp. dependence)

3.6 3.7 4.9

Pure SiC is colorless. The brown to black color of industrial product results from iron impurities. The rainbow-like luster of the crystals is caused by a passivation layer of silicon dioxide that forms on the surface.

The high sublimation temperature of SiC (approximately 2700 °C) makes it useful for bearings and furnace parts. Silicon carbide does not melt at any known pressure. It is also highly inert chemically. There is currently much interest in its use as a semiconductor material in electronics, where its high thermal conductivity, high electric field breakdown strength and high maximum current density make it more promising than silicon for high-powered devices.[31] SiC also has a very low coefficient of thermal expansion (4.0 × 10−6/K) and experiences no phase transitions that would cause discontinuities in thermal expansion.[

Electrical conductivity[edit]

Silicon carbide is a semiconductor, which can be doped n-type by nitrogen or phosphorus and p-type by beryllium, boron, aluminium, or gallium.[3] Metallic conductivity has been achieved by heavy doping with boron, aluminium or nitrogen.

Superconductivity has been detected in 3C-SiC:Al, 3C-SiC:B and 6H-SiC:B at the same temperature of 1.5 K.[29][32] A crucial difference is however observed for the magnetic field behavior between aluminium and boron doping: SiC:Al is type-II, same as Si:B. On the contrary, SiC:B is type-I. In attempt to explain this difference, it was noted that Si sites are more important than carbon sites for superconductivity in SiC. Whereas boron substitutes carbon in SiC, Al substitutes Si sites. Therefore, Al and B "see" different environment that might explain different properties of SiC:Al and SiC:B.[33]

Abrasive and cutting tools[edit]

In the arts, silicon carbide is a popular abrasive in modern lapidary due to the durability and low cost of the material. In manufacturing, it is used for its hardness in abrasive machining processes such as grinding, honing, water-jet cutting and sandblasting. Particles of silicon carbide are laminated to paper to create sandpapers and the grip tape on skateboards.[34]

In 1982 an exceptionally strong composite of aluminium oxide and silicon carbide whiskers was discovered. Development of this laboratory-produced composite to a commercial product took only three years. In 1985, the first commercial cutting tools made from this alumina and silicon carbide whisker-reinforced composite were introduced to the market.[35]

Structural material[edit]

In the 1980s and 1990s, silicon carbide was studied in several research programs for high-temperature gas turbines in Europe, Japan and the United States. The components were intended to replace nickel superalloy turbine blades or nozzle vanes. However, none of these projects resulted in a production quantity, mainly because of its low impact resistance and its low fracture toughness.[36]

Like other hard ceramics (namely alumina and boron carbide), silicon carbide is used in composite armor (e.g. Chobham armor), and in ceramic plates in bulletproof vests. Dragon Skin, which is produced by Pinnacle Armor, uses disks of silicon carbide.[37]

Silicon carbide is used as a support and shelving material in high temperature kilns such as for firing ceramics, glass fusing, or glass casting. SiC kiln shelves are considerably lighter and more durable than traditional alumina shelves.[38]

In December 2015, infusion of silicon carbide nano-particles in molten magnesium was mentioned as a way to produce a new strong and plastic alloy suitable for use in aeronautics, aerospace, automobile and micro-electronics.

The Porsche Carrera GT's carbon-ceramic (silicon carbide) disc brake

Automobile parts[edit]

Silicon-infiltrated carbon-carbon composite is used for high performance "ceramic" brake discs, as it is able to withstand extreme temperatures. The silicon reacts with the graphite in the carbon-carbon composite to become carbon-fiber-reinforced silicon carbide (C/SiC). These discs are used on some road-going sports cars, supercars, as well as other performance cars including the Porsche Carrera GT, the Bugatti Veyron, the Chevrolet Corvette ZR1, Bentleys, Ferraris, Lamborghinis, some specific high performance Audis, and the McLaren P1.[40] Silicon carbide is also used in a sintered form for diesel particulate filters.[41] SiC is also used as an oil additive to reduce friction, emissions, and harmonics.[42]

Electric systems[edit]

The earliest electrical application of SiC was in lightning arresters in electric power systems. These devices must exhibit high resistance until the voltage across them reaches a certain threshold VT at which point their resistance must drop to a lower level and maintain this level until the applied voltage drops below VT.[43]

It was recognized early on that SiC had such a voltage-dependent resistance, and so columns of SiC pellets were connected between high-voltage power lines and the earth. When a lightning strike to the line raises the line voltage sufficiently, the SiC column will conduct, allowing strike current to pass harmlessly to the earth instead of along the power line. Such SiC columns proved to conduct significantly at normal power-line operating voltages and thus had to be placed in series with a spark gap. This spark gap is ionized and rendered conductive when lightning raises the voltage of the power line conductor, thus effectively connecting the SiC column between the power conductor and the earth. Spark gaps used in lightning arresters are unreliable, either failing to strike an arc when needed or failing to turn off afterwards, in the latter case due to material failure or contamination by dust or salt. Usage of SiC columns was originally intended to eliminate the need for the spark gap in a lightning arrester. Gapped SiC lightning arresters were used as lightning-protection tool and sold under GE and Westinghouse brand names, among others. The gapped SiC arrester has been largely displaced by no-gap varistors that use columns of zinc oxide pellets.[44]

Electronic circuit elements[edit]

Ultraviolet LED

Power electronic devices[edit]

Silicon carbide is a semiconductor in research and early mass-production providing advantages for fast, high-temperature and/or high-voltage devices. The first devices available were Schottky diodes, followed by junction-gate FETs and MOSFETs for high-power switching. Bipolar transistors and thyristors are currently developed.[31] A major problem for SiC commercialization has been the elimination of defects: edge dislocations, screw dislocations (both hollow and closed core), triangular defects and basal plane dislocations.[45] As a result, devices made of SiC crystals initially displayed poor reverse blocking performance though researchers have been tentatively finding solutions to improve the breakdown performance.[46] Apart from crystal quality, problems with the interface of SiC with silicon dioxide have hampered the development of SiC-based power MOSFETs and insulated-gate bipolar transistors. Although the mechanism is still unclear, nitridation has dramatically reduced the defects causing the interface problems.[47] In 2008, the first commercial JFETs rated at 1200 V were introduced to the market,[48] followed in 2011 by the first commercial MOSFETs rated at 1200 V. Beside SiC switches and SiC Schottky diodes (also Schottky barrier diode, SBD) in the popular TO-247 and TO-220 packages, companies started even earlier to implement the bare chips into their power electronic modules. SiC SBD diodes found wide market spread being used in PFC circuits and IGBT power modules.[49] Conferences such as the International Conference on Integrated Power Electronics Systems (CIPS) report regularly about the technological progress of SIC power devices. Major challenges for fully unleashing the capabilities of SiC power devices are:

Gate drive: SiC devices often require gate drive voltage levels that are different from their silicon counterparts and may be even unsymmetric, for example, +20 V and −5 V.[50]

Packaging: SiC chips may have a higher power density than silicon power devices and are able to handle higher temperatures exceeding the silicon limit of 150 °C. New die attach technologies such as sintering are required to efficiently get the heat out of the devices and ensure a reliable interconnection.[51]

LEDs[edit]

The phenomenon of electroluminescence was discovered in 1907 using silicon carbide and the first commercial LEDs were again based on SiC. Yellow LEDs made from 3C-SiC were manufactured in the Soviet Union in the 1970s[52] and blue ones (6H-SiC) worldwide in the 1980s.[53] The production was soon stopped because gallium nitride showed 10–100 times brighter emission. This difference in efficiency is due to the unfavorable indirect bandgap of SiC, whereas GaN has a direct bandgap which favors light emission. However, SiC is still one of the important LED components – it is a popular substrate for growing GaN devices, and it also serves as a heat spreader in high-power LEDs.[53]

Astronomy[edit]

The low thermal expansion coefficient, high hardness, rigidity and thermal conductivity make silicon carbide a desirable mirror material for astronomical telescopes. The growth technology (chemical vapor deposition) has been scaled up to produce disks of polycrystalline silicon carbide up to 3.5 meters in diameter, and several telescopes like the Herschel Space Telescope are already equipped with SiC optics.[54][55]

Thin filament pyrometry[edit]

Main article: Thin filament pyrometry

Image of the test flame and glowing SiC fibers. The flame is about 7 cm tall.

Silicon carbide fibers are used to measure gas temperatures in an optical technique called thin filament pyrometry. It involves the placement of a thin filament in a hot gas stream. Radiative emissions from the filament can be correlated with filament temperature. Filaments are SiC fibers with a diameter of 15 micrometers, about one fifth that of a human hair. Because the fibers are so thin, they do little to disturb the flame and their temperature remains close to that of the local gas. Temperatures of about 800–2500 K can be measured.[56][57]

Heating elements[edit]

References to silicon carbide heating elements exist from the early 20th century when they were produced by Acheson's Carborundum Co. in the U.S. and EKL in Berlin. Silicon carbide offered increased operating temperatures compared with metallic heaters. Silicon carbide elements are used today in the melting of glass and non-ferrous metal, heat treatment of metals, float glass production, production of ceramics and electronics components, igniters in pilot lights for gas heaters, etc.[58]

Nuclear fuel particles[edit]

Silicon carbide is an important material in TRISO-coated fuel particles, the type of nuclear fuel found in high temperature gas cooled reactors such as the Pebble Bed Reactor. A layer of silicon carbide gives coated fuel particles structural support and is the main diffusion barrier to the release of fission products.

Nuclear fuel cladding[edit]

Silicon carbide composite material has been investigated for use as a replacement for Zircaloy cladding in light water reactors. The composite consists of SiC fibers wrapped around a SiC inner layer and surrounded by an SiC outer layer.[60] Problems have been reported with the ability to join the pieces of the SiC composite.[61]

Jewelry[edit]

A moissanite engagement ring

As a gemstone used in jewelry, silicon carbide is called "synthetic moissanite" or just "moissanite" after the mineral name. Moissanite is similar to diamond in several important respects: it is transparent and hard (9–9.5 on the Mohs scale, compared to 10 for diamond), with a refractive index between 2.65 and 2.69 (compared to 2.42 for diamond). Moissanite is somewhat harder than common cubic zirconia. Unlike diamond, moissanite can be strongly birefringent. For this reason, moissanite jewels are cut along the optic axis of the crystal to minimize birefringent effects. It is lighter (density 3.21 g/cm3 vs. 3.53 g/cm3), and much more resistant to heat than diamond. This results in a stone of higher luster, sharper facets and good resilience. Loose moissanite stones may be placed directly into wax ring moulds for lost-wax casting, as can diamond,[62] as moissanite remains undamaged by temperatures up to 1800 °C. Moissanite has become popular as a diamond substitute, and may be misidentified as diamond, since its thermal conductivity is closer to diamond than any other substitute. Many thermal diamond-testing devices cannot distinguish moissanite from diamond, but the gem is distinct in its birefringence and a very slight green or yellow fluorescence under ultraviolet light. Some moissanite stones also have curved, string-like inclusions, which diamonds never have.[63]

Steel production[edit]

Piece of silicon carbide used in steel making

Silicon carbide, dissolved in a basic oxygen furnace used for making steel, acts as a fuel. The additional energy liberated allows the furnace to process more scrap with the same charge of hot metal. It can also be used to raise tap temperatures and adjust the carbon and silicon content. Silicon carbide is cheaper than a combination of ferrosilicon and carbon, produces cleaner steel and less emissions due to low levels of trace elements, has a low gas content, and does not lower the temperature of steel.[64]

Catalyst support[edit]

The natural resistance to oxidation exhibited by silicon carbide, as well as the discovery of new ways to synthesize the cubic β-SiC form, with its larger surface area, has led to significant interest in its use as a heterogeneous catalyst support. This form has already been employed as a catalyst support for the oxidation of hydrocarbons, such as n-butane, to maleic anhydride.[65][66]

Carborundum printmaking[edit]

Silicon carbide is used in carborundum printmaking – a collagraph printmaking technique. Carborundum grit is applied in a paste to the surface of an aluminium plate. When the paste is dry, ink is applied and trapped in its granular surface, then wiped from the bare areas of the plate. The ink plate is then printed onto paper in a rolling-bed press used for intaglio printmaking. The result is a print of painted marks embossed into the paper.[67]

Graphene production[edit]

Silicon carbide is used to produce epitaxial graphene by graphitization at high temperatures. This is considered as one of the promising methods to synthesize graphene at large scale for practical applications.[68][69]

See

QMR Reaction bonded silicon carbide, also known as siliconized silicon carbide or SiSiC, is a type of silicon carbide that is manufactured by a chemical reaction between porous carbon or graphite with molten silicon. Due to the left over traces of silicon, reaction bonded silicon carbide is often referred to as siliconized silicon carbide, or its abbreviation SiSiC.

If pure silicon carbide is produced by sintering of silicon carbide powder, it usually contains traces of chemicals called sintering aids, which are added to support the sintering process by allowing lower sintering temperatures. This type of silicon carbide is often referred to as sintered silicon carbide, or abbreviated to SSiC.

The silicon carbide powder is gained from silicon carbide produced as described in the article silicon carbide.

QMRPandemic (2008), a cooperative board game in which the players have to discover the cures for four diseases that break out at the same time.

Quadrant Model of Reality

Monday, February 22, 2016

Quadrant Model of Reality Book 18 Silicon

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