diamond - wikipedia, the free encyclopedia

8/12/2019 Diamond - Wikipedia, The Free Encyclopedia

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3/22/2014 Diamond - Wikipedia, the free encyclopedia

http://en.wikipedia.org/wiki/Diamond 2

Diaphaneity Transparent to subtransparent to

translucent

Specific

gravity

3.52 0.01

Density 3.53.53 g/cm3

Polish luster Adamantine

Optical

properties

Isotropic

Refractive

index

2.418 (at 500 nm)

Birefringence None

Pleochroism None

Dispersion 0.044

Melting point Pressure dependent

References [1][2]

Contents

1 History1.1 Natural history

2 Material properties2.1 Hardness2.2 Electrical conductivity

2.3 Surface property2.4 Chemical stability2.5 Color2.6 Identification

3 Industry3.1 Gem-grade diamonds3.2 Industrial-grade diamonds3.3 Mining3.4 Political issues

4 Synthetics, simulants, and enhancements4.1 Synthetics4.2 Simulants4.3 Enhancements4.4 Identification

5 Stolen diamonds6 See also7 References8 Books9 External links

History

See also: Diamond (gemstone)

The name diamondis derived from the ancient Greek (admas), "proper", "unalterable", "unbreakable","untamed", from - (a-), "un-" + (dam), "I overpower", "I tame".[3]Diamonds are thought to have beenfirst recognized and mined in India, where significant alluvial deposits of the stone could be found many centuries

ago along the rivers Penner, Krishna and Godavari. Diamonds have been known in India for at least 3,000 yearsbut most likely 6,000 years.[4]

Diamonds have been treasured as gemstones since their use as religious icons in ancient India. Their usage inengraving tools also dates to early human history.[5][6]The popularity of diamonds has risen since the 19th century

because of increased supply, improved cutting and polishing techniques, growth in the world economy, andinnovative and successful advertising campaigns.[7]
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One face of an uncut octahedral

diamond, showing trigons (of positiv

and negative relief) formed by natura

chemical etching

In 1772, Antoine Lavoisier used a lens to concentrate the rays of the sun on a diamond in an atmosphere ofoxygen, and showed that the only product of the combustion was carbon dioxide, proving that diamond iscomposed of carbon.[8]Later in 1797, Smithson Tennant repeated and expanded that experiment.[9]Bydemonstrating that burning diamond and graphite releases the same amount of gas he established the chemicalequivalence of these substances.[10]

The most familiar use of diamonds today is as gemstones used for adornment, a use which dates back into antiquitThe dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds. In the20th century, experts in gemology have developed methods of grading diamonds and other gemstones based on thcharacteristics most important to their value as a gem. Four characteristics, known informally as thefour Cs, arenow commonly used as the basic descriptors of diamonds: these are carat, cut, color, and clarity.[11]A large,flawless diamond is known as a paragon.

Natural history

The formation of natural diamond requires very specific conditionsexposure of carbon-bearing materials to highpressure, ranging approximately between 45 and 60 kilobars (4.5 and 6 GPa), but at a comparatively low

temperature range between approximately 900 and 1,300 C (1,650 and 2,370 F). These conditions are met intwo places on Earth; in the lithospheric mantle below relatively stable continental plates, and at the site of ameteorite strike.[12]

Formation in cratons

The conditions for diamond formation to happen in the lithosphericmantle occur at considerable depth corresponding to the requirements oftemperature and pressure. These depths are estimated between 140 and190 kilometers (87 and 118 mi) though occasionally diamonds have

crystallized at depths about 300 kilometers (190 mi).[13]The rate atwhich temperature changes with increasing depth into the Earth variesgreatly in different parts of the Earth. In particular, under oceanic platesthe temperature rises more quickly with depth, beyond the range requiredfor diamond formation at the depth required. The correct combination oftemperature and pressure is only found in the thick, ancient, and stable

parts of continental plates where regions of lithosphere known as cratonsexist. Long residence in the cratonic lithosphere allows diamond crystalsto grow larger.[13]

Through studies of carbon isotope ratios (similar to the methodologyused in carbon dating, except with the stable isotopes C-12 and C-13), it has been shown that the carbon found indiamonds comes from both inorganic and organic sources. Some diamonds, known as harzburgitic, are formedfrom inorganic carbon originally found deep in the Earth's mantle. In contrast, eclogiticdiamonds contain organiccarbon from organic detritus that has been pushed down from the surface of the Earth's crust through subduction(see plate tectonics) before transforming into diamond. These two different source of carbon have measurablydifferent 13C:12C ratios. Diamonds that have come to the Earth's surface are generally quite old, ranging from unde1 billion to 3.3 billion years old. This is 22% to 73% of the age of the Earth. [13]
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Diamonds occur most often as euhedral or rounded octahedra and twinned octahedra known as macles. Asdiamond's crystal structure has a cubic arrangement of the atoms, they have many facets that belong to a cube,octahedron, rhombicosidodecahedron, tetrakis hexahedron or disdyakis dodecahedron. The crystals can haverounded off and unexpressive edges and can be elongated. Sometimes they are found grown together or formdouble "twinned" crystals at the surfaces of the octahedron. These different shapes and habits of some diamondsresult from differing external circumstances. Diamonds (especially those with rounded crystal faces) are commonlyfound coated in nyf, an opaque gum-like skin.[14]

Space diamonds

See also: Aggregated diamond nanorod

Primitive interstellar meteorites were found to contain carbon possibly in the form of diamond (Lewis et al.1987).[15]Not all diamonds found on Earth originated here. A type of diamond called carbonado that is found inSouth America and Africa may have been deposited there via an asteroid impact (not formed from the impact)about 3 billion years ago. These diamonds may have formed in the intrastellar environment, but as of 2008, therewas no scientific consensus on how carbonado diamonds originated.[16][17]

Diamonds can also form under other naturally occurring high-pressure conditions. Very small diamonds ofmicrometer and nanometer sizes, known as microdiamondsor nanodiamondsrespectively, have been found inmeteorite impact craters. Such impact events create shock zones of high pressure and temperature suitable fordiamond formation. Impact-type microdiamonds can be used as an indicator of ancient impact craters.[12]Popigacrater in Russia may have the world's largest diamond deposit, estimated at trillions of carats, and formed by anasteroid impact.[18]

Scientific evidence indicates that white dwarf stars have a core of crystallized carbon and oxygen nuclei. The largeof these found in the universe so far, BPM 37093, is located 50 light-years (4.7 1014km) away in the

constellation Centaurus. A news release from the Harvard-Smithsonian Center for Astrophysics described the2,500-mile (4,000 km)-wide stellar core as a diamond.[19]It was referred to asLucy, after the Beatles' song"Lucy in the Sky With Diamonds".[20][21]

Transport from mantle

Diamond-bearing rock is carried from the mantle to the Earth's surface by deep-origin volcanic eruptions. Themagma for such a volcano must originate at a depth where diamonds can be formed[13]150 km (93 mi) or mor(three times or more the depth of source magma for most volcanoes). This is a relatively rare occurrence. Thesetypically small surface volcanic craters extend downward in formations known as volcanic pipes.[13]The pipescontain material that was transported toward the surface by volcanic action, but was not ejected before the volcanactivity ceased. During eruption these pipes are open to the surface, resulting in open circulation; many xenoliths osurface rock and even wood and fossils are found in volcanic pipes. Diamond-bearing volcanic pipes are closelyrelated to the oldest, coolest regions of continental crust (cratons). This is because cratons are very thick, and theirlithospheric mantle extends to great enough depth that diamonds are stable. Not all pipes contain diamonds, andeven fewer contain enough diamonds to make mining economically viable.[13]Diamonds are very rare[22]becausemost of the crust is too thin to permit diamond crystallisation, whereas most of the mantle has relatively little carbon
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Schematic diagram of a volcanic pipe

Theoretically predicted phase diagram

of carbon

Diamond and graphite are two

allotropes of carbon: pure forms of

the same element that differ in

structure.

The magma in volcanic pipes is usually one of two characteristic types,which cool into igneous rock known as either kimberlite or lamproite.[13]

The magma itself does not contain diamond; instead, it acts as an elevatorthat carries deep-formed rocks (xenoliths), minerals (xenocrysts), andfluids upward. These rocks are characteristically rich in magnesium-

bearing olivine, pyroxene, and amphibole minerals[13]which are oftenaltered to serpentine by heat and fluids during and after eruption. Certain

indicator mineralstypically occur within diamantiferous kimberlites andare used as mineralogical tracers by prospectors, who follow theindicator trail back to the volcanic pipe which may contain diamonds.These minerals are rich in chromium (Cr) or titanium (Ti), elements whichimpart bright colors to the minerals. The most common indicator mineralsare chromium garnets (usually bright red chromium-pyrope, andoccasionally green ugrandite-series garnets), eclogitic garnets, orangetitanium-pyrope, red high-chromium spinels, dark chromite, bright greenchromium-diopside, glassy green olivine, black picroilmenite, and magnetite. Kimberlite deposits are known as bluroundfor the deeper serpentinized part of the deposits, or asyellow groundfor the near surface smectite clay

and carbonate weathered and oxidized portion.[13]

Once diamonds have been transported to the surface by magma in a volcanic pipe, they may erode out and bedistributed over a large area. A volcanic pipe containing diamonds is known as aprimary sourceof diamonds.Secondary sourcesof diamonds include all areas where a significant number of diamonds have been eroded out otheir kimberlite or lamproite matrix, and accumulated because of water or wind action. These include alluvialdeposits and deposits along existing and ancient shorelines, where loose diamonds tend to accumulate because oftheir size and density. Diamonds have also rarely been found in deposits left behind by glaciers (notably inWisconsin and Indiana); in contrast to alluvial deposits, glacial deposits are minor and are therefore not viablecommercial sources of diamond.[13]

Material properties

Main articles: Material properties of diamond and Crystallographic defects in diamond

A diamond is a transparentcrystal of tetrahedrally bondedcarbon atoms in a covalentnetwork lattice (sp3) thatcrystallizes into the diamond

lattice which is a variation ofthe face centered cubicstructure. Diamonds have beenadapted for many uses

because of the material'sexceptional physicalcharacteristics. Most notableare its extreme hardness and

thermal conductivity (9002,320 Wm1K1),[23]as well as widebandgap and high optical dispersion.[24]Above 1,700 C (1,973 K / 3,583 F) in vacuum or oxygen-free
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The extreme hardness of diamond in

certain orientations makes it useful in

materials science, as in this pyramida

diamond embedded in the working

surface of a Vickers hardness tester.

atmosphere, diamond converts to graphite; in air, transformation starts at ~700 C.[25]Diamond's ignition point is720 800 C in oxygen and 850 1,000 C in air.[26]Naturally occurring diamonds have a density ranging from3.153.53 g/cm3, with pure diamond close to 3.52 g/cm3.[1]The chemical bonds that hold the carbon atoms indiamonds together are weaker than those in graphite. In diamonds, the bonds form an inflexible three-dimensionallattice, whereas in graphite, the atoms are tightly bonded into sheets, which can slide easily over one another,

making the overall structure weaker.[27]

Hardness

Diamond is the hardest known natural material on the Mohs scale of mineral hardness, where hardness is defined resistance to scratching and is graded between 1 (softest) and 10 (hardest). Diamond has a hardness of 10(hardest) on this scale.[28]Diamond's hardness has been known since antiquity, and is the source of its name.

Diamond hardness depends on its purity, crystalline perfection and orientation: hardness is higher for flawless, purecrystals oriented to the direction (along the longest diagonal of the cubic diamond lattice). [29]Therefore,whereas it might be possible to scratch some diamonds with other materials, such as boron nitride, the hardestdiamonds can only be scratched by other diamonds and nanocrystalline diamond aggregates.

The hardness of diamond contributes to its suitability as a gemstone. Because it can only be scratched by otherdiamonds, it maintains its polish extremely well. Unlike many other gems, it is well-suited to daily wear because ofits resistance to scratchingperhaps contributing to its popularity as the preferred gem in engagement or weddingrings, which are often worn every day.

The hardest natural diamonds mostly originate from the Copeton andBingara fields located in the New England area in New South Wales,Australia. These diamonds are generally small, perfect to semiperfectoctahedra, and are used to polish other diamonds. Their hardness is

associated with the crystal growth form, which is single-stage crystalgrowth. Most other diamonds show more evidence of multiple growthstages, which produce inclusions, flaws, and defect planes in the crystallattice, all of which affect their hardness. It is possible to treat regulardiamonds under a combination of high pressure and high temperature to

produce diamonds that are harder than the diamonds used in hardnessgauges.[20]

Somewhat related to hardness is another mechanical propertytoughness, which is a material's ability to resist breakage from forceful

impact. The toughness of natural diamond has been measured as 7.510MPam1/2.[30][31]This value is good compared to other gemstones, but poor compared to most engineeringmaterials. As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage.Diamond has a cleavage plane and is therefore more fragile in some orientations than others. Diamond cutters usethis attribute to cleave some stones, prior to faceting.[32]"Impact toughness" is one of the main indexes to measurethe quality of synthetic industrial diamonds.[26]

Electrical conductivity
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Brown diamonds at the National Museum of NaturaHistory in Washington, D.C.

Other specialized applications also exist or are being developed, including use as semiconductors: some bluediamonds are natural semiconductors, in contrast to most diamonds, which are excellent electrical insulators. [33]

The conductivity and blue color originate from boron impurity. Boron substitutes for carbon atoms in the diamondlattice, donating a hole into the valence band.[33]

Substantial conductivity is commonly observed in nominally undoped diamond grown by chemical vapor depositioThis conductivity is associated with hydrogen-related species adsorbed at the surface, and it can be removed byannealing or other surface treatments.[34][35]

Surface property

Diamonds are naturally lipophilic and hydrophobic, which means the diamonds' surface cannot be wet by water bucan be easily wet and stuck by oil. This property can be utilized to extract diamonds using oil when makingsynthetic diamonds.[26]However, when diamond surfaces are chemically modified with certain ions, they areexpected to become so hydrophilic that they can stabilize multiple layers of water ice at human bodytemperature.[36]

Chemical stability

Diamonds are not very reactive. Under room temperature diamonds do not react with any chemical reagentsincluding strong acids and bases. A diamond's surface can only be oxidized a little by just a few oxidants at hightemperature (below 1,000 C). Therefore, acids and bases can be used to refine synthetic diamonds. [26]

Color

Main article: Diamond color

Diamond has a wide bandgap of 5.5 eV corresponding tothe deep ultraviolet wavelength of 225 nanometers. Thismeans pure diamond should transmit visible light and appearas a clear colorless crystal. Colors in diamond originatefrom lattice defects and impurities. The diamond crystallattice is exceptionally strong and only atoms of nitrogen,

boron and hydrogen can be introduced into diamond duringthe growth at significant concentrations (up to atomic

percents). Transition metals Ni and Co, which arecommonly used for growth of synthetic diamond by high-

pressure high-temperature techniques, have been detectedin diamond as individual atoms; the maximum concentrationis 0.01% for Ni[37]and even much less for Co. Virtuallyany element can be introduced to diamond by ion implantation.[38]

Nitrogen is by far the most common impurity found in gem diamonds and is responsible for the yellow and browncolor in diamonds. Boron is responsible for the blue color.[24]Color in diamond has two additional sources:irradiation (usually by alpha particles), that causes the color in green diamonds; and plastic deformation of thediamond crystal lattice. Plastic deformation is the cause of color in some brown[39]and perhaps pink and red
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A round brilliant cut diamond set

in a ring

diamonds.[40]In order of rarity, yellow diamond is followed by brown, colorless, then by blue, green, black, pink,orange, purple, and red.[32]"Black", or Carbonado, diamonds are not truly black, but rather contain numerousdark inclusions that give the gems their dark appearance. Colored diamonds contain impurities or structural defectthat cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most diamondimpurities replace a carbon atom in the crystal lattice, known as a carbon flaw. The most common impurity,nitrogen, causes a slight to intense yellow coloration depending upon the type and concentration of nitrogen

present.[32]The Gemological Institute of America (GIA) classifies low saturation yellow and brown diamonds as

diamonds in the normal color range, and applies a grading scale from "D" (colorless) to "Z" (light yellow).Diamonds of a different color, such as blue, are calledfancy coloreddiamonds, and fall under a different gradingscale.[32]

In 2008, the Wittelsbach Diamond, a 35.56-carat (7.112 g) blue diamond once belonging to the King of Spain,fetched over US$24 million at a Christie's auction.[41]In May 2009, a 7.03-carat (1.406 g) blue diamond fetchedthe highest price per carat ever paid for a diamond when it was sold at auction for 10.5 million Swiss francs(6.97 million euro or US$9.5 million at the time).[42]That record was however beaten the same year: a 5-carat(1.0 g) vivid pink diamond was sold for $10.8 million in Hong Kong on December 1, 2009. [43]

Identification

Diamonds can be identified by their high thermal conductivity. Their high refractive index is also indicative, but othmaterials have similar refractivity. Diamonds cut glass, but this does not positively identify a diamond because othematerials, such as quartz, also lie above glass on the Mohs scale and can also cut it. Diamonds can scratch otherdiamonds, but this can result in damage to one or both stones. Hardness tests are infrequently used in practicalgemology because of their potentially destructive nature.[28]The extreme hardness and high value of diamondmeans that gems are typically polished slowly using painstaking traditional techniques and greater attention to detaithan is the case with most other gemstones;[10]these tend to result in extremely flat, highly polished facets withexceptionally sharp facet edges. Diamonds also possess an extremely high refractive index and fairly high

dispersion. Taken together, these factors affect the overall appearance of a polished diamond and mostdiamantaires still rely upon skilled use of a loupe (magnifying glass) to identify diamonds 'by eye'.[44]

Industry

See also: Diamonds as an investment

The diamond industry can be separated into two distinct categories: onedealing with gem-grade diamonds and another for industrial-grade

diamonds. Both markets value diamonds differently.

Gem-grade diamonds

Main article: Diamond (gemstone)

A large trade in gem-grade diamonds exists. Unlike other commodities, suchas most precious metals, there is a substantial mark-up in the retail sale ofgem diamonds.[45]There is a well-established market for resale of polisheddiamonds (e.g. pawnbroking, auctions, second-hand jewelry stores,
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diamantaires, bourses, etc.). One hallmark of the trade in gem-quality diamonds is its remarkable concentration:wholesale trade and diamond cutting is limited to just a few locations; in 2003, 92% of the world's diamonds werecut and polished in Surat, India.[46]Other important centers of diamond cutting and trading are the Antwerpdiamond district in Belgium, where the International Gemological Institute is based, London, the Diamond District i

New York City, Tel Aviv, and Amsterdam. A single company De Beers controls a significant proportion of thtrade in diamonds.[47]They are based in Johannesburg, South Africa and London, England. One contributoryfactor is the geological nature of diamond deposits: several large primary kimberlite-pipe mines each account for

significant portions of market share (such as the Jwaneng mine in Botswana, which is a single large pit operated byDe Beers that can produce between 12,500,000 carats (2,500 kg) to 15,000,000 carats (3,000 kg) of diamondsper year,[48]) whereas secondary alluvial diamond deposits tend to be fragmented amongst many differentoperators because they can be dispersed over many hundreds of square kilometers (e.g., alluvial deposits in Brazil

The production and distribution of diamonds is largely consolidated in the hands of a few key players, andconcentrated in traditional diamond trading centers, the most important being Antwerp, where 80% of all roughdiamonds, 50% of all cut diamonds and more than 50% of all rough, cut and industrial diamonds combined arehandled.[49]This makes Antwerp a de facto "world diamond capital".[50]Another important diamond center is

New York City, where almost 80% of the world's diamonds are sold, including auction sales.[49]The DeBeers

company, as the world's largest diamond miner holds a dominant position in the industry, and has done so sincesoon after its founding in 1888 by the British imperialist Cecil Rhodes. De Beers owns or controls a significantportion of the world's rough diamond production facilities (mines) and distribution channels for gem-qualitydiamonds. The Diamond Trading Company (DTC) is a subsidiary of De Beers and markets rough diamonds fromDe Beers-operated mines. De Beers and its subsidiaries own mines that produce some 40% of annual worlddiamond production. For most of the 20th century over 80% of the world's rough diamonds passed through DeBeers,[51]but by 20012009 the figure had decreased to around 45%, [52]and by 2013 the company's marketshare had further decreased to around 38% in value terms and even less by volume.[53]De Beers sold off the vastmajority of its diamond stockpile in the late 1990s early 2000s[54]and the remainder largely represents workingstock (diamonds that are being sorted before sale).[55]This was well documented in the press[56]but remains little

known to the general public.

As a part of reducing its influence, De Beers withdrew from purchasing diamonds on the open market in 1999 andceased, at the end of 2008, purchasing Russian diamonds mined by the largest Russian diamond companyAlrosa.[57]As of January 2011, De Beers states that it only sells diamonds from the following four countries:Botswana, Namibia, South Africa and Canada.[58]Alrosa had to suspend their sales in October 2008 due to theglobal energy crisis,[59]but the company reported that it had resumed selling rough diamonds on the open market

by October 2009.[60]Apart from Alrosa, other important diamond mining companies include BHP Billiton, which the world's largest mining company;[61]Rio Tinto Group, the owner of Argyle (100%), Diavik (60%), and Murow(78%) diamond mines;[62]and Petra Diamonds, the owner of several major diamond mines in Africa.

Further down the supply chain, members of The World Federation of Diamond Bourses (WFDB) act as a mediumfor wholesale diamond exchange, trading both polished and rough diamonds. The WFDB consists of independentdiamond bourses in major cutting centers such as Tel Aviv, Antwerp, Johannesburg and other cities across theUSA, Europe and Asia.[32]In 2000, the WFDB and The International Diamond Manufacturers Associationestablished the World Diamond Council to prevent the trading of diamonds used to fund war and inhumane acts.WFDB's additional activities include sponsoring the World Diamond Congress every two years, as well as theestablishment of theInternational Diamond Council(IDC) to oversee diamond grading.
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Diamond polisher in Amsterdam

Once purchased by Sightholders (which is a trademark term referring tothe companies that have a three-year supply contract with DTC),diamonds are cut and polished in preparation for sale as gemstones('industrial' stones are regarded as a by-product of the gemstone market;they are used for abrasives).[63]The cutting and polishing of roughdiamonds is a specialized skill that is concentrated in a limited number oflocations worldwide.[63]Traditional diamond cutting centers are

Antwerp, Amsterdam, Johannesburg, New York City, and Tel Aviv.Recently, diamond cutting centers have been established in China, India,Thailand, Namibia and Botswana.[63]Cutting centers with lower cost oflabor, notably Surat in Gujarat, India, handle a larger number of smallercarat diamonds, while smaller quantities of larger or more valuable diamonds are more likely to be handled inEurope or North America. The recent expansion of this industry in India, employing low cost labor, has allowedsmaller diamonds to be prepared as gems in greater quantities than was previously economically feasible. [49]

Diamonds which have been prepared as gemstones are sold on diamond exchanges called bourses. There are 28registered diamond bourses in the world.[64]Bourses are the final tightly controlled step in the diamond supply

chain; wholesalers and even retailers are able to buy relatively small lots of diamonds at the bourses, after whichthey are prepared for final sale to the consumer. Diamonds can be sold already set in jewelry, or sold unset("loose"). According to the Rio Tinto Group, in 2002 the diamonds produced and released to the market werevalued at US$9 billion as rough diamonds, US$14 billion after being cut and polished, US$28 billion in wholesalediamond jewelry, and US$57 billion in retail sales.[65]

Cutting

Main articles: Diamond cutting and Diamond cut

Mined rough diamonds are converted into gems through a multi-step process called "cutting". Diamonds areextremely hard, but also brittle and can be split up by a single blow. Therefore, diamond cutting is traditionallyconsidered as a delicate procedure requiring skills, scientific knowledge, tools and experience. Its final goal is to

produce a faceted jewel where the specific angles between the facets would optimize the diamond luster, that isdispersion of white light, whereas the number and area of facets would determine the weight of the final product.The weight reduction upon cutting is significant and can be of the order of 50%. [66]Several possible shapes areconsidered, but the final decision is often determined not only by scientific, but also practical considerations. Forexample the diamond might be intended for display or for wear, in a ring or a necklace, singled or surrounded byother gems of certain color and shape.[67]

The most time-consuming part of the cutting is the preliminary analysis of the rough stone. It needs to address alarge number of issues, bears much responsibility, and therefore can last years in case of unique diamonds. Thefollowing issues are considered:

The hardness of diamond and its ability to cleave strongly depend on the crystal orientation. Therefore, thecrystallographic structure of the diamond to be cut is analyzed using X-ray diffraction to choose the optimalcutting directions.Most diamonds contain visible non-diamond inclusions and crystal flaws. The cutter has to decide whichflaws are to be removed by the cutting and which could be kept.The diamond can be split by a single, well calculated blow of a hammer to a pointed tool, which is quick, bu
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The Darya-I-Nur Diamondanexample of unusual diamond cut and

jewelry arrangement

risky. Alternatively, it can be cut with a diamond saw, which is a

more reliable but tedious procedure.[67][68]

After initial cutting, the diamond is shaped in numerous stages ofpolishing. Unlike cutting, which is a responsible but quick operation,polishing removes material by gradual erosion and is extremely timeconsuming. The associated technique is well developed; it is consideredas a routine and can be performed by technicians.[69]After polishing, thediamond is reexamined for possible flaws, either remaining or induced bythe process. Those flaws are concealed through various diamondenhancement techniques, such as repolishing, crack filling, or cleverarrangement of the stone in the jewelry. Remaining non-diamondinclusions are removed through laser drilling and filling of the voids

produced.[28]

Marketing

Marketing has significantly affected the image of diamond as a valuablecommodity.

N. W. Ayer & Son, the advertising firm retained by De Beers in the mid-20th century, succeeded in reviving the American diamond market. And the firm created new markets in countrieswhere no diamond tradition had existed before. N. W. Ayer's marketing included product placement, advertisingfocused on the diamond product itself rather than the De Beers brand, and associations with celebrities and royaltyWithout advertising the De Beers brand, De Beers was also advertising its competitors' diamond products aswell[70](De Beers' market share dipped temporarily to 2nd place in the global market below Alrosa in theaftermath of the global economic crisis of 2008, down to less than 29% in terms of carats mined, rather than

sold[71]). The campaign lasted for decades but was effectively discontinued by early 2011. De Beers still advertisediamonds, but the advertising now mostly promotes its own brands, or licensed product lines, rather thancompletely "generic" diamond products.[71]The campaign was perhaps best captured by the slogan "a diamond isforever".[7]This slogan is now being used by De Beers Diamond Jewelers,[72]a jewelry firm which is a 50%/50%oint venture between the De Beers mining company and LVMH, the luxury goods conglomerate.

Brown-colored diamonds constituted a significant part of the diamond production, and were predominantly usedfor industrial purposes. They were seen as worthless for jewelry (not even being assessed on the diamond colorscale). After the development of Argyle diamond mine in Australia in 1986, and marketing, brown diamonds have

become acceptable gems.[73][74]The change was mostly due to the numbers: the Argyle mine, with its 35,000,000

carats (7,000 kg) of diamonds per year, makes about one-third of global production of natural diamonds; [75]80%of Argyle diamonds are brown.[76]

Industrial-grade diamonds

Industrial diamonds are valued mostly for their hardness and thermal conductivity, making many of the gemologicacharacteristics of diamonds, such as the 4 Cs, irrelevant for most applications. 80% of mined diamonds (equal toabout 135,000,000 carats (27,000 kg) annually), are unsuitable for use as gemstones, and used industrially.[77]In
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A scalpel with synthetic diamond

blade

Close-up photograph of an angle

grinder blade with tiny diamonds

shown embedded in the metal

addition to mined diamonds, synthetic diamonds found industrial applications almost immediately after theirinvention in the 1950s; another 570,000,000 carats (114,000 kg) of synthetic diamond is produced annually forindustrial use. Approximately 90% of diamond grinding grit is currently of synthetic origin. [78]

The boundary between gem-quality diamonds and industrial diamonds ispoorly defined and partly depends on market conditions (for example, ifdemand for polished diamonds is high, some lower-grade stones will be

polished into low-quality or small gemstones rather than being sold forindustrial use). Within the category of industrial diamonds, there is a sub-category comprising the lowest-quality, mostly opaque stones, which areknown as bort.[79]

Industrial use of diamonds has historically been associated with theirhardness, which makes diamond the ideal material for cutting andgrinding tools. As the hardest known naturally occurring material,diamond can be used to polish, cut, or wear away any material, includingother diamonds. Common industrial applications of this property includediamond-tipped drill bits and saws, and the use of diamond powder as

an abrasive. Less expensive industrial-grade diamonds, known as bort,with more flaws and poorer color than gems, are used for such

purposes.[80]Diamond is not suitable for machining ferrous alloys at highspeeds, as carbon is soluble in iron at the high temperatures created byhigh-speed machining, leading to greatly increased wear on diamondtools compared to alternatives.[81]

Specialized applications include use in laboratories as containment forhigh pressure experiments (see diamond anvil cell), high-performance

bearings, and limited use in specialized windows.[79]With the continuingadvances being made in the production of synthetic diamonds, futureapplications are becoming feasible. The high thermal conductivity ofdiamond makes it suitable as a heat sink for integrated circuits inelectronics.[82]

Mining

See also: List of diamond mines and Exploration diamond

drilling

Approximately 130,000,000 carats (26,000 kg) of diamonds are mined annually, with a total value of nearlyUS$9 billion, and about 100,000 kg (220,000 lb) are synthesized annually.[83]

Roughly 49% of diamonds originate from Central and Southern Africa, although significant sources of the mineralhave been discovered in Canada, India, Russia, Brazil, and Australia.[78]They are mined from kimberlite andlamproite volcanic pipes, which can bring diamond crystals, originating from deep within the Earth where high

pressures and temperatures enable them to form, to the surface. The mining and distribution of natural diamonds asubjects of frequent controversy such as concerns over the sale of blood diamondsor conflict diamondsby
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A diamond knife blade used for

cutting ultrathin sections (typically 70

to 350 nm for transmission electron

microscopy.

Siberia's Udachnaya diamond mine

African paramilitary groups.[84]The diamond supply chain is controlledby a limited number of powerful businesses, and is also highlyconcentrated in a small number of locations around the world.

Only a very small fraction of the diamond ore consists of actualdiamonds. The ore is crushed, during which care is required not todestroy larger diamonds, and then sorted by density. Today, diamondsare located in the diamond-rich density fraction with the help of X-rayfluorescence, after which the final sorting steps are done by hand. Beforethe use of X-rays became commonplace,[66]the separation was donewith grease belts; diamonds have a stronger tendency to stick to greasethan the other minerals in the ore.[32]

Historically, diamonds were found only in alluvial deposits in Guntur andKrishna district of the Krishna River delta in Southern India.[85]India ledthe world in diamond production from the time of their discovery inapproximately the 9th century BC[4][86]to the mid-18th century AD, but

the commercial potential of these sources had been exhausted by the late18th century and at that time India was eclipsed by Brazil where the firstnon-Indian diamonds were found in 1725.[4]Currently, one of the most

prominent Indian mines is located at Panna.[87]

Diamond extraction from primary deposits (kimberlites and lamproites)started in the 1870s after the discovery of the Diamond Fields in SouthAfrica.[88]Production has increased over time and now an accumulatedtotal of 4,500,000,000 carats (900,000 kg) have been mined since thatdate.[89]Twenty percent of that amount has been mined in the last five years, and during the last 10 years, nine new

mines have started production; four more are waiting to be opened soon. Most of these mines are located inCanada, Zimbabwe, Angola, and one in Russia.[89]

In the U.S., diamonds have been found in Arkansas, Colorado, Wyoming, and Montana. [90][91]In 2004, thediscovery of a microscopic diamond in the U.S. led to the January 2008 bulk-sampling of kimberlite pipes in aremote part of Montana.[91]

Today, most commercially viable diamond deposits are in Russia (mostly in Sakha Republic, for example Mir pipeand Udachnaya pipe), Botswana, Australia (Northern and Western Australia) and the Democratic Republic ofCongo.[92]In 2005, Russia produced almost one-fifth of the global diamond output, reports the British Geological

Survey. Australia boasts the richest diamantiferous pipe, with production from the Argyle diamond mine reachingpeak levels of 42 metric tons per year in the 1990s.[90][93]There are also commercial deposits being actively minein the Northwest Territories of Canada and Brazil.[78]Diamond prospectors continue to search the globe fordiamond-bearing kimberlite and lamproite pipes.

Political issues

Main articles: Kimberley Process, Blood diamond, and Child labour in the diamond industry
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Unsustainable diamond mining in

Sierra Leone

(http://en.wikibooks.org/wiki/Develop

ment_Cooperation_Handbook/Stories

Unsustainable_Growth)

Synthetic diamonds of various colorsgrown by the high-pressure high-

temperature technique

In some of the more politically unstable central African and west African countries, revolutionary groups have takecontrol of diamond mines, using proceeds from diamond sales to finance their operations. Diamonds sold throughthis process are known as conflict diamondsor blood diamonds.[84]

Major diamond trading corporations continue to fund and fuel theseconflicts by doing business with armed groups. In response to publicconcerns that their diamond purchases were contributing to war andhuman rights abuses in central and western Africa, the United Nations,the diamond industry and diamond-trading nations introduced theKimberley Process in 2002.[94]The Kimberley Process aims to ensurethat conflict diamonds do not become intermixed with the diamonds notcontrolled by such rebel groups. This is done by requiring diamond-

producing countries to provide proof that the money they make fromselling the diamonds is not used to fund criminal or revolutionaryactivities. Although the Kimberley Process has been moderatelysuccessful in limiting the number of conflict diamonds entering the market,some still find their way in. Conflict diamonds constitute 23% of alldiamonds traded.[95]Two major flaws still hinder the effectiveness of the Kimberley Process: (1) the relative ease

of smuggling diamonds across African borders, and (2) the violent nature of diamond mining in nations that are notin a technical state of war and whose diamonds are therefore considered "clean".[94]

The Canadian Government has set up a body known as Canadian Diamond Code of Conduct[96]to helpauthenticate Canadian diamonds. This is a stringent tracking system of diamonds and helps protect the "conflictfree" label of Canadian diamonds.[97]

Synthetics, simulants, and enhancements

Synthetics

Main article: Synthetic diamond

Synthetic diamonds are diamonds manufactured in a laboratory, asopposed to diamonds mined from the Earth. The gemological andindustrial uses of diamond have created a large demand for rough stones.This demand has been satisfied in large part by synthetic diamonds,which have been manufactured by various processes for more than half acentury. However, in recent years it has become possible to producegem-quality synthetic diamonds of significant size.[13]It is possible tomake colorless synthetic gemstones that, on a molecular level, areidentical to natural stones and so visually similar that only a gemologistwith special equipment can tell the difference.[98]

The majority of commercially available synthetic diamonds are yellow and are produced by so-called High PressurHigh Temperature (HPHT) processes.[99]The yellow color is caused by nitrogen impurities. Other colors may als

be reproduced such as blue, green or pink, which are a result of the addition of boron or from irradiation aftersynthesis.[100]
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Colorless gem cut from diamond

grown by chemical vapor deposition

Gem-cut synthetic silicon carbide setin a ring

Another popular method of growing synthetic diamond is chemical vapordeposition (CVD). The growth occurs under low pressure (belowatmospheric pressure). It involves feeding a mixture of gases (typically 1to 99 methane to hydrogen) into a chamber and splitting them tochemically active radicals in a plasma ignited by microwaves, hotfilament, arc discharge, welding torch or laser.[101]This method is mostlyused for coatings, but can also produce single crystals several millimeters

in size (see picture).

[83]

As of 2010, nearly all 5,000 million carats (1,000 tonnes) of syntheticdiamonds produced per year are for industrial use. Around 50% of the133 million carats of natural diamonds mined per year end up in industrialuse.[98][102]The cost of mining a natural colorless diamond runs about$40 to $60 per carat, and the cost to produce a synthetic, gem-qualitycolorless diamond is about $2,500 per carat.[98]However, a purchaseris more likely to encounter a synthetic when looking for a fancy-colored diamond because nearly all syntheticdiamonds are fancy-colored, while only 0.01% of natural diamonds are. [103]

Simulants

Main article: Diamond simulant

A diamond simulant is a non-diamond material that is used to simulate theappearance of a diamond, and may be referred to as diamante. Cubiczirconia is the most common. The gemstone Moissanite (silicon carbide)can be treated as a diamond simulant, though more costly to producethan cubic zirconia. Both are produced synthetically.[104]

Enhancements

Main article: Diamond enhancement

Diamond enhancements are specific treatments performed on natural or synthetic diamonds (usually those alreadycut and polished into a gem), which are designed to better the gemological characteristics of the stone in one ormore ways. These include laser drilling to remove inclusions, application of sealants to fill cracks, treatments toimprove a white diamond's color grade, and treatments to give fancy color to a white diamond. [105]

Coatings are increasingly used to give a diamond simulant such as cubic zirconia a more "diamond-like"appearance. One such substance is diamond-like carbonan amorphous carbonaceous material that has somephysical properties similar to those of the diamond. Advertising suggests that such a coating would transfer some othese diamond-like properties to the coated stone, hence enhancing the diamond simulant. Techniques such asRaman spectroscopy should easily identify such a treatment.[106]

Identification
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Early diamond identification tests included a scratch test relying on the superior hardness of diamond. This test isdestructive, as a diamond can scratch diamond, and is rarely used nowadays. Instead, diamond identification relieson its superior thermal conductivity. Electronic thermal probes are widely used in the gemological centers toseparate diamonds from their imitations. These probes consist of a pair of battery-powered thermistors mounted ia fine copper tip. One thermistor functions as a heating device while the other measures the temperature of thecopper tip: if the stone being tested is a diamond, it will conduct the tip's thermal energy rapidly enough to producea measurable temperature drop. This test takes about 23 seconds.[107]

Whereas the thermal probe can separate diamonds from most of their simulants, distinguishing between varioustypes of diamond, for example synthetic or natural, irradiated or non-irradiated, etc., requires more advanced,optical techniques. Those techniques are also used for some diamonds simulants, such as silicon carbide, which

pass the thermal conductivity test. Optical techniques can distinguish between natural diamonds and syntheticdiamonds. They can also identify the vast majority of treated natural diamonds.[108]"Perfect" crystals (at the atomilattice level) have never been found, so both natural and synthetic diamonds always possess characteristicimperfections, arising from the circumstances of their crystal growth, that allow them to be distinguished from eachother.[109]

Laboratories use techniques such as spectroscopy, microscopy and luminescence under shortwave ultraviolet lightto determine a diamond's origin.[108]They also use specially made instruments to aid them in the identification

process. Two screening instruments are theDiamondSureand theDiamondView, both produced by the DTC anmarketed by the GIA.[110]

Several methods for identifying synthetic diamonds can be performed, depending on the method of production andthe color of the diamond. CVD diamonds can usually be identified by an orange fluorescence. D-J coloreddiamonds can be screened through the Swiss Gemmological Institute's[111]Diamond Spotter. Stones in the D-Zcolor range can be examined through the DiamondSure UV/visible spectrometer, a tool developed by DeBeers.[109]Similarly, natural diamonds usually have minor imperfections and flaws, such as inclusions of foreign

material, that are not seen in synthetic diamonds.Screening devices based on diamond type detection can be used to make a distinction between diamonds that arecertainly natural and diamonds that are potentially synthetic. Those potentially synthetic diamonds require moreinvestigation in a specialized lab. Examples of commercial screening devices are D-Screen (WTOCD / HRDAntwerp) and Alpha Diamond Analyzer (Bruker / HRD Antwerp).

Stolen diamonds

Occasionally large thefts of diamonds take place. In February 2013 armed robbers carried out a raid at Brussels

Airport and escaped with gems estimated to be worth $50m (32m; 37m euros). The gang broke through aperimeter fence and raided the cargo hold of a Swiss-bound plane. The gang have since been arrested and largeamounts of cash and diamonds recovered.[112]

The identification of stolen diamonds presents a set of difficult problems. Rough diamonds will have a distinctiveshape depending on whether their source is a mine or from an alluvial environment such as a beach or river - alluvidiamonds have smoother surfaces than those that have been mined. Determining the provenance of cut and polishestones is much more complex.
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The Kimberley Process was developed to monitor the trade in rough diamonds and prevent their being used to funviolence. Before exporting, rough diamonds are certificated by the government of the country of origin. Somecountries, such as Venezuela, are not party to the agreement. The Kimberley Process does not apply to local salesof rough diamonds within a country.

Diamondsmay be etched by laser with marks invisible to the naked eye. Lazare Kaplan, a US-based company,developedthis method. However, whatever is marked on a diamond can readily be removed. [113][114]

See also

Listof diamondsListof minerals

References

1. ^ ab"Diamond" (http://www.mindat.org/min-1282.html). Mindat. Retrieved 2009-07-07.2. ^"Diamond" (http://webmineral.com/data/Diamond.shtml). WebMineral. Retrieved 2009-07-07.3. ^Liddell, H.G.; Scott, R. "Adamas" (http://www.perseus.tufts.edu/cgi-bin/ptext?

doc=Perseus%3Atext%3A1999.04.0057%3Aentry%3D%231145). A Greek-English Lexicon. Perseus Project.

4. ^ abcHershey, W. (1940). The Book of Diamonds(http://books.google.com/?id=35eij1e1al8C&pg=PA23). NewYork: Hearthside Press. pp. 2228. ISBN 1-4179-7715-9.

5. ^Pliny the Elder (2004).Natural History: A Selection. Penguin Books. p. 371. ISBN 0-14-044413-0.6. ^"Chinese made first use of diamond" (http://news.bbc.co.uk/2/hi/science/nature/4555235.stm). BBC News.

2005-05-17. Retrieved 2007-03-21.

7. ^ abEpstein, E.J. (1982). "Have You Ever Tried To Sell a Diamond?"(http://www.theatlantic.com/issues/82feb/8202diamond1.htm). The Atlantic. Retrieved 2009-05-05.

8. ^See:Lavoisier (1772) "Premier mmoire sur la destruction du diamant par le feu"(http://gallica.bnf.fr/ark:/12148/bpt6k35711/f739.image) (First memoir on the destruction of diamond byfire),Histoire de l'Acadmie royale des sciences. Avec les Mmoires de Mathmatique & de Physique(History of the Royal Academy of Sciences. With the Memoirs of Mathematics and Physics), part 2, 564-591.Lavoisier (1772) "Second mmoire sur la destruction du diamant par le feu"(http://gallica.bnf.fr/ark:/12148/bpt6k35711/f766.image) (Second memoir on the destruction of diamond bfire),Histoire de l'Acadmie royale des sciences. Avec les Mmoires de Mathmatique & de Physique, par2, 591-616.

9. ^Smithson Tennant (1797) "On the nature of the diamond," (http://books.google.com/books?id=vlBFAAAAcAAJ&pg=PA123#v=onepage&q&f=false)Philosophical Transactions of the Royal Society of

London, 87: 123-127.

10. ^ abHazen, R. M (1999). The diamond makers(http://books.google.com/?id=fNJQok6N9_MC&pg=PA7).Cambridge University Press. pp. 710. ISBN 0-521-65474-2.

11. ^Hesse, R. W. (2007).Jewelrymaking through history(http://books.google.com/?id=DIWEi5Hg93gC&pg=PA42Greenwood Publishing Group. p. 42. ISBN 0-313-33507-9.

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71. ^ abJCK Staff (2011-01-26). "10 Things Rocking the Industry" (http://www.jckonline.com/2011/01/26/10-thingrocking-industry).JCK. Jckonline.com. Retrieved 2012-09-09.

72. ^Bates, Rob (2011-01-14). "Interview with Forevermark CEO" (http://www.jckonline.com/blogs/cutting-remarks/2011/01/14/interview-forevermark-ceo). JCK. Jckonline.com. Retrieved 2012-09-09.

73. ^Harlow, George E. (1998). The nature of diamonds(http://books.google.com/?id=_WI86J88ydAC&pg=PA34).Cambridge University Press. p. 34. ISBN 0-521-62935-7.

74. ^Kogel, Jessica Elzea (2006).Industrial minerals & rocks (http://books.google.com/?id=zNicdkuulE4C&pg=PA416). Soc iety for Mining, Metallurgy, and Exploration (U.S.). p. 416. ISBN 0-87335-

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