Quartz
Quartz crystal cluster from Tibet
General
Category	Silicate mineral
Chemical formula	Silica (silicon dioxide, SiO2)
Strunz classification	04.DA.05
Dana classification	75.01.03.01
Crystal symmetry	Trigonal H–M Symbol 32
Unit cell	a = 4.9133 Å, c = 5.4053 Å; Z = 3
Identification
Color	From colorless to black, through various colors
Crystal habit	6-sided prism ending in 6-sided pyramid (typical), drusy, fine-grained to microcrystalline, massive
Crystal system	α-quartz: trigonal trapezohedral class 3 2; β-quartz: hexagonal 622[1]
Twinning	Common Dauphine law, Brazil law and Japan law
Cleavage	{0110} Indistinct
Fracture	Conchoidal
Tenacity	Brittle
Mohs scale hardness	7 – lower in impure varieties (defining mineral)
Luster	Vitreous – waxy to dull when massive
Streak	White
Diaphaneity	Transparent to nearly opaque
Specific gravity	2.65; variable 2.59–2.63 in impure varieties
Optical properties	Uniaxial (+)
Refractive index	nω = 1.543–1.545 nε = 1.552–1.554
Birefringence	+0.009 (B-G interval)
Pleochroism	None
Melting point	1670 °C (β tridymite) 1717 °C (β cristobalite)[1]
Solubility	Insoluble at STP; 1 ppmmass at 400 °C and 34 bar to 2600 ppmmass at 500 °C and 103 bar[1]
Other characteristics	Piezoelectric, may be triboluminescent, chiral (hence optically active if not racemic)
References	[2][3][4][5]

Quartz is an abundant mineral in the Earth's continental crust. It is made up of a continuous framework of SiO₄ silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO₂. There are many different varieties of quartz, several of which are semi-precious gemstones. Throughout the world, varieties of quartz have been, since antiquity, the most commonly used minerals in the making of jewelry and hardstone carvings.

Crystal habit and structure[link]

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, but because the crystals must be attached at the other end to a matrix, only one termination pyramid is present. There are exceptions as doubly terminated crystals do occur. An occurrence in Herkimer County, New York is noted for these Herkimer diamonds with terminations at both ends. 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 and β-quartz[link]

Crystal structure of α-quartz

β-quartz

α-quartz crystallizes in the trigonal crystal system, space group P3₁21 or P3₂21. β-quartz belongs to the hexagonal system, space group P6₂22 or P6₄22.^[6] 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, this process is called the quartz inversion.

Occurrence[link]

Quartz is an essential 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 also a common constituent of schist, gneiss, quartzite and other metamorphic rocks. Because of its resistance to weathering it is very common in stream sediments and in residual soils. Quartz, therefore, occupies the lowest potential to weather in the Goldich dissolution series.

Quartz occurs in hydrothermal veins as gangue along with ore minerals. Large crystals of quartz are found in pegmatites. Well-formed crystals may reach several meters in length and weigh as much as 1,400 pounds (640 kg).^[7]

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.^[8]

Related silica minerals[link]

Tridymite and cristobalite are high-temperature polymorphs of SiO₂ that occur in high-silica volcanic rocks. Coesite is a denser polymorph of quartz found in some meteorite impact sites and in metamorphic rocks formed at pressures greater than those typical of the Earth's crust. Stishovite and Seifertite are yet denser and higher-pressure polymorphs of quartz found in some meteorite impact sites. Lechatelierite is an amorphous silica glass SiO₂ which is formed by lightning strikes in quartz sand.

Synthetic quartz[link]

Most quartz used in microelectronics is produced synthetically. Large, flawless and untwinned crystals are produced in an autoclave via the hydrothermal process. The process involves treating crushed natural quartz with hot aqueous solution of a base such as sodium hydroxide. The hydroxide serves as a "mineralizer", i.e. it helps dissolve the "nutrient" quartz. High temperatures are required, often around 675 °C. The dissolved quartz then recrystallizes at a seed crystal at slightly lower temperatures. Approximately 200 tons of quartz were produced in the US in 2005; large synthesis facilities exist throughout the world. Synthetic quartz is often evaluated on the basis of its Q factor, a measure of its piezoelectric response and an indicator of the purity of the crystal.^[9]

A synthetic silicon dioxide crystal grown by the hydrothermal method, about 19 cm long and weighing about 127 grams

High-temperature glass composed of silicon dioxide with no (or only small amounts of) other components is referred to as "quartz glass" or fused quartz, although it is amorphous in structure, rather than crystalline.

Uses[link]

Quartz is the source of many silicon compounds such as silicones (e.g. high performance polymers), silicon (e.g. microelectronics), and many other compounds of commercial importance. Quartz in the form of sand is reduced by carbothermic reaction as a first step in these energy-intensive processes.

Owing to its high thermal and chemical stability and abundance, quartz is widely used in many large-scale applications related to abrasives, foundry materials, ceramics, and cements.^[9]

Piezoelectricity[link]

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. A common piezoelectric use 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. Quartz's piezoelectric properties were discovered by Jacques and Pierre Curie in 1880. The quartz oscillator or resonator was first developed by Walter Guyton Cady in 1921.^[10] George Washington Pierce designed and patented quartz crystal oscillators in 1923.^[11] Warren Marrison created the first quartz oscillator clock based on the work of Cady and Pierce in 1927.^[12]

Gemstone and lapidary varieties[link]

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).

Coarsely crystalline varieties[link]

Pure quartz, traditionally called rock crystal (sometimes called clear quartz), is colorless and transparent or translucent. Common colored varieties include citrine, rose quartz, amethyst, smoky quartz and milky quartz.

Citrine[link]

Citrine

Citrine is a variety of quartz whose color ranges from a pale yellow to brown. Natural citrines are rare; most commercial citrines are heat-treated amethyst. Citrine contains traces of Fe³⁺ and is rarely found naturally. The name is derived from Latin citrina which means "yellow".^[13]

Rose quartz[link]

Rose quartz crystals, Minas Gerais

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 types of quartz contain 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.^[14]

In crystal form (rarely found) it is called pink quartz and its color 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, US, but most crystals on the market come from Minas Gerais, Brazil.^[15]

Amethyst[link]

Amethyst is a form of quartz that ranges from a bright to dark or dull purple color.

Smoky quartz[link]

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.

Milky quartz[link]

Milky quartz sample

Milky quartz may be the most common variety of crystalline quartz and can be found almost anywhere. The white color may be caused by minute fluid inclusions of gas, liquid, or both, trapped during the crystal formation. The cloudiness caused by the inclusions effectively bars its use in most optical and quality gemstone applications.^[16]

Microcrystalline varieties[link]

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.^[17] Other opaque gemstone varieties of quartz, or mixed rocks including quartz, often including contrasting bands or patterns of color, are agate, onyx, carnelian, and jasper.

Varieties (according to microstructure)[link]

Although many of the varietal names historically arose from the color of the mineral, current scientific naming schemes refer primarily to the microstructure of the mineral. Color is a secondary identifier for the cryptocrystalline minerals, although it is a primary identifier for the macrocrystalline varieties. This does not always hold true.

Synthetic and artificial treatments[link]

Not all varieties of quartz are naturally occurring. 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.

History of naming and usage[link]

Quartz crystal showing transparency

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")).^[18] 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 the Republic of 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]

Roman naturalist Pliny the Elder believed quartz to be water ice, permanently frozen after great lengths of time. (The word "crystal" comes from the Greek word 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. He also knew of the ability of quartz to split light into a spectrum. This idea persisted until at least the 17th century.

In the 17th century, Nicolas Steno's study of quartz paved the way for modern crystallography. He discovered that no matter how distorted a quartz crystal, the long prism faces always made a perfect 60° angle.

Charles B. Sawyer invented the commercial quartz crystal manufacturing process in Cleveland, Ohio, United States. This initiated the transition from mined and cut quartz for electrical appliances to manufactured quartz.

See also[link]

Wikisource has original text related to this article: 1911 Encyclopædia Britannica/Quartz

• Fused quartz
• List of minerals
• Shocked quartz
• Quartz reef mining
• Flint

References[link]

External links[link]

Wikimedia Commons has media related to: Quartz

• Quartz varieties, properties, crystal morphology. Photos and illustrations
• Arkansas quartz, Rockhounding Arkansas
• Gilbert Hart Nomenclature of Silica, American Mineralogist, Volume 12, pages 383–395, 1927
• Queensland University of Technology Origin of the word quartz.
• PDF of Charles Sawyer's cultured quartz process description
• "The Quartz Watch – Inventors". The Lemelson Center, National Museum of American History. Smithsonian Institution. http://invention.smithsonian.org/centerpieces/quartz/inventors/index.html. 
• Terminology used to describe the characteristics of Quartz Crystals when used as oscillators
• A follow-up study of miners exposed to unusual concentrations of quartz by BG Miller and others. Institute of Occupational Medicine Research Report TM/95/03
• Further studies on the importance of quartz in the development of coalworkers’ pneumoconiosis by JMG Davis and others. Institute of Occupational Medicine Research Report TM/91/05

James May
James May in 2006
Born	James Daniel May (1963-01-16) 16 January 1963 (age 49)[1] Bristol, England
Residence	Hammersmith, West London, England
Nationality	British
Other names	Captain Slow
Education	Caerleon Endowed Junior School Oakwood Comprehensive School
Alma mater	Pendle College, Lancaster University
Occupation	Broadcaster, journalist, author, pianist, media personality
Years active	1998 (1998)–present (present)
Employer	BBC, The Daily Telegraph, (prev. Channel 4, ITV & Sky)
Known for	Presenting: Driven, Top Gear, Oz and James's Big Wine Adventure, Oz and James Drink to Britain, James May's Top Toys, James May's Toy Stories, James May's 20th Century, James May's Big Ideas, James May's Man Lab
Home town	Bristol, England
Height	1.85 m (6 ft 1 in)
Partner	Sarah Frater (2000–present)
Website
http://www.topgear.com/uk/james-may

This article may contain too much repetition or redundant language. Please help improve it by merging similar text or removing repeated statements. (May 2011)

James Daniel May (born 16 January 1963) is an English television presenter, journalist and writer. He is best known for his role as co-presenter of the award-winning motoring program Top Gear alongside Jeremy Clarkson , and Richard Hammond.

On Top Gear, May has the nickname "Captain Slow" for his careful driving style, a love of small underpowered cars and habit of getting lost and distracted while driving. However, in a July 2010 episode of Top Gear he drove a Bugatti Veyron Super Sport, reaching a speed of 417.6 kilometres per hour (259.5 mph).^[2] After his attempt the Bugatti test driver Pierre-Henri Raphanel took the car to 430 kilometers per hour (267.5 mph).

May has presented a variety of other programs on themes including science and technology, toys, cars, wine culture, and the plight of manliness in modern times. In addition he has released a variety of DVDs and books with similar themes, and wrote a weekly column for The Daily Telegraph's motoring section.

Early life[link]

James May was born in Bristol, one of four children; he has two sisters and a brother.^[3] May attended Caerleon Endowed Junior School in Newport, then in Monmouthshire. He spent his teenage years in South Yorkshire where he attended Oakwood Comprehensive School in Rotherham and was a choirboy at Whiston Parish Church.^[4] He was also at school with Life On Mars and Ashes to Ashes star Dean Andrews.^[5] A keen flautist and pianist, he later studied music at Pendle College, Lancaster University. After graduating, May briefly worked at a hospital in Chelsea as a records officer, and had a short stint in Her Majesty's Civil Service.^[6]

Personal life[link]

May lives in Hammersmith, London with dance critic Sarah Frater, whom he has dated since 2000.^[7][8]

May has owned a number of cars: Bentley T2, Rolls-Royce Phantom, Triumph 2000, Rover P6, Alfa Romeo 164, 1971 Rolls-Royce Corniche, Jaguar XJS, Range Rover, Fiat Panda, Datsun 120Y, Vauxhall Cavalier Mk1, Ferrari F430, 1984 Porsche 911,^[9] 2005 Porsche Boxster S (which he claims is the first car he has ever purchased new),^[10] Mini Cooper, Citroën Ami, Mazda MX-5 and several classic motorcycles including a Yamaha XJR1300, Moto Guzzi V11 Sport, a Triumph Daytona 675R and a 1978 Guzzi California. He has a penchant for prestige cars like Rolls-Royces and Bentleys, simple and basic cars such as the Fiat Panda, and motorcycles. He often uses a Brompton folding bicycle for commuting.^[11] He passed his driving test on his second attempt and justified this by saying "All the best people pass the second time".^[12]

May obtained a light aircraft pilot's licence in October 2006 having trained at White Waltham Airfield. He has owned a Luscombe 8A 'Silvaire' and an American Champion 8KCAB Super Decathlon.

May received an honorary Doctor of Letters degree from Lancaster University on 15 July 2010. ^[13]

Journalism[link]

During the early 1980s, May worked as a sub-editor for The Engineer and later Autocar magazine, from which he was dismissed. He has since written for several publications, including a regular column called England Made Me in Car Magazine, articles for Top Gear magazine, and a weekly column in The Daily Telegraph.

He has written a book titled May On Motors, which is a collection of his published articles, and co-authored Oz and James's Big Wine Adventure, based on the TV series of the same name.

He has also written the afterword to Long Lane with Turnings, published in September 2006, the final book by motoring writer L. J. K. Setright. In the same month he co-presented a tribute to Raymond Baxter. His book, Notes From The Hard Shoulder, was published on 26 April 2007. James May's 20th Century, a book to accompany the television series of the same name, was published on 6 September 2007.

[edit] Dismissal from Autocar

In an interview with Richard Allinson on BBC Radio 2,^[14] May confessed that he was fired in 1992 from Autocar magazine after putting together a hidden message or acrostic in one issue. At the end of the year, the magazine's "Road Test Year Book" supplement was published. Each spread featured four reviews and each review started with a large red letter (known in typography as an initial). May's role was to put the entire supplement together, which "was extremely boring and took several months". He went on to say:

So I had this idea that if I re-edited the beginnings of all the little texts, I could make these red letters spell out a message through the magazine, which I thought was brilliant. I can't remember exactly what it said, but it was to the effect that "You might think this is a really great thing, but if you were sitting here making it up you'd realise it's a real pain in the arse". It took me about two months to do it and on the day that it came out I'd actually forgotten that I'd done it because there's a bit of a gap between it being "put to bed" and coming out on the shelves. When I arrived at work that morning everybody was looking at their shoes and I was summoned to the managing director of the company's office. The thing had come out and nobody at work had spotted what I'd done because I'd made the words work around the pages so you never saw a whole word. But all the readers had seen it and they'd written in thinking they'd won a prize or a car or something.

May's original message, punctuated appropriately, reads: "So you think it's really good, yeah? You should try making the bloody thing up; it's a real pain in the arse."^[15]

This was referenced by Jeremy Clarkson during episode 2 of series 17 (in the course of the "hot hatch"-challenge in Italy) when May was noting Autocar's opinion on the Renault Clio Cup he had chosen for the challenge, to which Clarkson replied "Autocar.... The magazine that sacked you...?"

Radio and television[link]

His past television credits include presenting Driven on Channel 4 in 1998-99, narrating an eight-part BBC One series called Road Rage School,^[16] and co-hosting the ITV1 coverage of the 2006 London Boat Show.^[17] He also wrote and presented a Christmas special called James May's Top Toys (for BBC One) exploring the toys of his childhood.^[18] This list was followed up the next year by a sequel of sorts, broadcast on BBC Two, entitled James May: My Sister's Top Toys, this time attempting to investigate the gender divide of toy appeal.^[19] In series 3, episode 3^[20] of Gordon Ramsay's The F Word, May managed to beat Ramsay in eating animal penises and rotten shark (which Ramsay himself couldn't keep down)^[21] and with his fish pie recipe.^[22][23]

[edit] Top Gear

May first co-presented Top Gear in 1999, before it was axed by the BBC because of poor viewing figures. He rejoined the show in the second series of the present Top Gear format in 2003, where he earned the nickname "Captain Slow" owing to his careful driving style. Despite this sobriquet, he has done some especially high-speed driving, including in Top Gear Series 9, taking a Bugatti Veyron to its top speed of 253 mph (407 km/h) which is nearly one-third of the speed of sound at sea level and later on taking a Bugatti Veyron 16.4 Super Sport edition to 260 mph (417 km/h). In an earlier episode he also tested the original version of the Bugatti Veyron against the new Pagani Zonda F. On the show he claimed that it was 'a piece of cake' driving those cars, but seconds later Jeremy Clarkson played a tape showing him spinning wildly over the test track in the Zonda. Originally he did not want to do this test, but Clarkson had hurt his neck in the previous episode while driving a truck through a brick wall and Richard Hammond claimed that he was busy selling fish at Morrisons. He is often mocked for a poor sense of direction, shown getting lost many times throughout the course of the series, including race tracks and even being mocked once by Jeremy and Hammond for mistaking a normal Range Rover as the camera crew. He also flew in a Royal Air Force Eurofighter Typhoon at a speed of around 1320 mph for his television programme, James May's 20th Century. He also became one of the first people – with co-presenter Jeremy Clarkson and an Icelandic support crew – to travel by car to the magnetic North Pole, using a modified Toyota Hilux. He claims to be the first person on the north pole who didn't want to go there. He was also one of the first people to drive across the Makgadikgadi salt plains in Botswana.^[24] He has driven a 1.3 litre Suzuki SJ413 through the Bolivian jungle and along Death Road and over the Andes to the Pacific Ocean in Chile. He also drove a modified Toyota Hilux (also used as a crew car during the North Pole expedition) up the side of the erupting volcano Eyjafjallajökull in Iceland.

Science[link]

May has also presented a documentary for Sky about sharks called Inside Killer Sharks and a series looking at inventions and discoveries during the twentieth century, entitled James May's 20th Century.^[25] In late 2008, the BBC broadcast James May's Big Ideas, a three-part series in which May travelled around the globe in search of implementations for concepts widely considered science fiction.^[26]

[edit] James May on the Moon

In June 2009 May presented a documentary on BBC Two called James May on the Moon commemorating 40 years since man first landed on the moon.^[27] This was followed by another documentary on BBC Four called James May at the Edge of Space, where May was flown to the edge of space (70,000 ft) in a U.S. Air Force Lockheed U-2 spy plane. Highlights of the footage from the training for the flight, and the flight itself was used in James May on the Moon, but was shown fully in this programme.^[28] This made him one of the highest flying persons, along with the pilot, at that time, after the crew of the International Space Station.^[28]

[edit] James May's Toy Stories

Beginning in October 2009, May presented a 6-part TV series showing favourite toys of the past era and whether they can be applied in the modern day. The toys featured were Airfix, Plasticine, Meccano, Scalextric, Lego and Hornby. In each show, May attempts to take each toy to its limits, also fulfilling several of his boyhood dreams in the process. For example, in August 2009, May built a full-sized house out of Lego at Denbies Wine Estate in Surrey.^[29] Plans for Legoland to move it to their theme park fell through in September 2009 because costs to deconstruct, move and then rebuild were too high^[30] and despite a final Facebook appeal for someone to take it, it was demolished on 22 September, with the plastic bricks planned to be donated to charity.^[31] Also for the series, he recreated the banked track at Brooklands using Scalextric track,^[32] and an attempt at the world's longest working model railway along the Tarka Trail between Barnstaple and Bideford in North Devon, although the attempt was foiled due to stolen batteries and vandals placing coins on the track, causing a short circuit.^[33]

Drink[link]

In late 2006, the BBC broadcast Oz and James's Big Wine Adventure, a series in which May, a committed bitter drinker, travelled around France with wine expert Oz Clarke.^[34] A second series was broadcast in late 2007, this time with May and Clarke in the Californian wine country,^[35] and was followed by a third series in 2009 called Oz and James Drink to Britain.

Career[link]

Television[link]

DVD[link]

Books[link]

References[link]

External links[link]

• Telegraph Motoring - James May's weekly column
• James May at the Internet Movie Database
• James May on Top Gear
• Daily Mail article on May