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Diamonds are far from evenly distributed over the Earth. A rule of thumb known as Clifford's rule states that they are almost always found in kimberlites on the oldest part of cratons , the stable cores of continents with typical ages of 2.
The Argyle diamond mine in Australia , the largest producer of diamonds by weight in the world, is located in a mobile belt , also known as an orogenic belt ,  a weaker zone surrounding the central craton that has undergone compressional tectonics.
Instead of kimberlite, the host rock is lamproite. Lamproites with diamonds that are not economically viable are also found in the United States, India and Australia.
Kimberlites can be found in narrow 1 to 4 meters dikes and sills, and in pipes with diameters that range from about 75 m to 1.
Fresh rock is dark bluish green to greenish gray, but after exposure rapidly turns brown and crumbles. They are a mixture of xenocrysts and xenoliths minerals and rocks carried up from the lower crust and mantle , pieces of surface rock, altered minerals such as serpentine , and new minerals that crystallized during the eruption.
The texture varies with depth. The composition forms a continuum with carbonatites , but the latter have too much oxygen for carbon to exist in a pure form.
Instead, it is locked up in the mineral calcite Ca C O 3. All three of the diamond-bearing rocks kimberlite, lamproite and lamprophyre lack certain minerals melilite and kalsilite that are incompatible with diamond formation.
In kimberlite, olivine is large and conspicuous, while lamproite has Ti- phlogopite and lamprophyre has biotite and amphibole.
They are all derived from magma types that erupt rapidly from small amounts of melt, are rich in volatiles and magnesium oxide , and are less oxidizing than more common mantle melts such as basalt.
These characteristics allow the melts to carry diamonds to the surface before they dissolve. Kimberlite pipes can be difficult to find.
They weather quickly within a few years after exposure and tend to have lower topographic relief than surrounding rock. If they are visible in outcrops, the diamonds are never visible because they are so rare.
In any case, kimberlites are often covered with vegetation, sediments, soils or lakes. In modern searches, geophysical methods such as aeromagnetic surveys , electrical resistivity and gravimetry , help identify promising regions to explore.
This is aided by isotopic dating and modeling of the geological history. Then surveyors must go to the area and collect samples, looking for kimberlite fragments or indicator minerals.
The latter have compositions that reflect the conditions where diamonds form, such as extreme melt depletion or high pressures in eclogites.
However, indicator minerals can be misleading; a better approach is geothermobarometry , where the compositions of minerals are analyzed as if they were in equilibrium with mantle minerals.
Finding kimberlites requires persistence, and only a small fraction contain diamonds that are commercially viable. The only major discoveries since about have been in Canada.
Since existing mines have lifetimes of as little as 25 years, there could be a shortage of new diamonds in the future. Diamonds are dated by analyzing inclusions using the decay of radioactive isotopes.
Depending on the elemental abundances, one can look at the decay of rubidium to strontium , samarium to neodymium , uranium to lead , argon to argon , or rhenium to osmium.
Those found in kimberlites have ages ranging from 1 to 3. The kimberlites themselves are much younger. Most of them have ages between tens of millions and million years old, although there are some older exceptions Argyle, Premier and Wawa.
Thus, the kimberlites formed independently of the diamonds and served only to transport them to the surface. The reason for the lack of older kimberlites is unknown, but it suggests there was some change in mantle chemistry or tectonics.
No kimberlite has erupted in human history. Such depths occur below cratons in mantle keels , the thickest part of the lithosphere.
These regions have high enough pressure and temperature to allow diamonds to form and they are not convecting, so diamonds can be stored for billions of years until a kimberlite eruption samples them.
Host rocks in a mantle keel include harzburgite and lherzolite , two type of peridotite. The most dominant rock type in the upper mantle , peridotite is an igneous rock consisting mostly of the minerals olivine and pyroxene ; it is low in silica and high in magnesium.
However, diamonds in peridotite rarely survive the trip to the surface. They formed in eclogite but are distinguished from diamonds of shallower origin by inclusions of majorite a form of garnet with excess silicon.
Diamond is thermodynamically stable at high pressures and temperatures, with the phase transition from graphite occurring at greater temperatures as the pressure increases.
Thus, the deeper origin of some diamonds may reflect unusual growth environments. In the first known natural samples of a phase of ice called Ice VII were found as inclusions in diamond samples.
The mantle has roughly one billion gigatonnes of carbon for comparison, the atmosphere-ocean system has about 44, gigatonnes.
It can also be altered by surface processes like photosynthesis. This variability implies that they are not formed from carbon that is primordial having resided in the mantle since the Earth formed.
Instead, they are the result of tectonic processes, although given the ages of diamonds not necessarily the same tectonic processes that act in the present.
Diamonds in the mantle form through a metasomatic process where a C-O-H-N-S fluid or melt dissolves minerals in a rock and replaces them with new minerals.
Diamonds form from this fluid either by reduction of oxidized carbon e. Using probes such as polarized light, photoluminescence and cathodoluminescence , a series of growth zones can be identified in diamonds.
The characteristic pattern in diamonds from the lithosphere involves a nearly concentric series of zones with very thin oscillations in luminescence and alternating episodes where the carbon is resorbed by the fluid and then grown again.
Diamonds from below the lithosphere have a more irregular, almost polycrystalline texture, reflecting the higher temperatures and pressures as well as the transport of the diamonds by convection.
Geological evidence supports a model in which kimberlite magma rose at 4—20 meters per second, creating an upward path by hydraulic fracturing of the rock.
As the pressure decreases, a vapor phase exsolves from the magma, and this helps to keep the magma fluid.
Then, at lower pressures, the rock is eroded, forming a pipe and producing fragmented rock breccia. As the eruption wanes, there is pyroclastic phase and then metamorphism and hydration produces serpentinites.
Although diamonds on Earth are rare, they are very common in space. In meteorites , about three percent of the carbon is in the form of nanodiamonds , having diameters of a few nanometers.
Sufficiently small diamonds can form in the cold of space because their lower surface energy makes them more stable than graphite.
The isotopic signatures of some nanodiamonds indicate they were formed outside the Solar System in stars. High pressure experiments predict that large quantities of diamonds condense from methane into a "diamond rain" on the ice giant planets Uranus and Neptune.
Diamonds may exist in carbon-rich stars, particularly white dwarfs. One theory for the origin of carbonado , the toughest form of diamond, is that it originated in a white dwarf or supernova.
The most familiar uses of diamonds today are as gemstones used for adornment , and as industrial abrasives for cutting hard materials.
The markets for gem-grade and industrial-grade diamonds value diamonds differently. The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds.
In the 20th century, experts in gemology developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem.
Four characteristics, known informally as the four Cs , are now commonly used as the basic descriptors of diamonds: these are its mass in carats a carat being equal to 0.
A large, flawless diamond is known as a paragon. A large trade in gem-grade diamonds exists. Although most gem-grade diamonds are sold newly polished, there is a well-established market for resale of polished diamonds e.
Secondary alluvial diamond deposits, on the other hand, tend to be fragmented amongst many different operators because they can be dispersed over many hundreds of square kilometers e.
The De Beers company, as the world's largest diamond mining company, holds a dominant position in the industry, and has done so since soon after its founding in by the British imperialist Cecil Rhodes.
De Beers is currently the world's largest operator of diamond production facilities mines and distribution channels for gem-quality diamonds.
As a part of reducing its influence, De Beers withdrew from purchasing diamonds on the open market in and ceased, at the end of , purchasing Russian diamonds mined by the largest Russian diamond company Alrosa.
Further down the supply chain, members of The World Federation of Diamond Bourses WFDB act as a medium for wholesale diamond exchange, trading both polished and rough diamonds.
Once purchased by Sightholders which is a trademark term referring to the 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.
Recently, diamond cutting centers have been established in China, India, Thailand , Namibia and Botswana. The recent expansion of this industry in India, employing low cost labor, has allowed smaller diamonds to be prepared as gems in greater quantities than was previously economically feasible.
Diamonds prepared as gemstones are sold on diamond exchanges called bourses. There are 28 registered diamond bourses in the world.
Diamonds can be sold already set in jewelry, or sold unset "loose". Mined rough diamonds are converted into gems through a multi-step process called "cutting".
Diamonds are extremely hard, but also brittle and can be split up by a single blow. Therefore, diamond cutting is traditionally considered 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 is dispersion of white light, whereas the number and area of facets would determine the weight of the final product.
For example, the diamond might be intended for display or for wear, in a ring or a necklace, singled or surrounded by other gems of certain color and shape.
Some of them are special, produced by certain companies, for example, Phoenix , Cushion , Sole Mio diamonds, etc.
The most time-consuming part of the cutting is the preliminary analysis of the rough stone. It needs to address a large number of issues, bears much responsibility, and therefore can last years in case of unique diamonds.
The following issues are considered:. After initial cutting, the diamond is shaped in numerous stages of polishing. Unlike cutting, which is a responsible but quick operation, polishing removes material by gradual erosion and is extremely time consuming.
The associated technique is well developed; it is considered as a routine and can be performed by technicians.
Those flaws are concealed through various diamond enhancement techniques, such as repolishing, crack filling, or clever arrangement of the stone in the jewelry.
Remaining non-diamond inclusions are removed through laser drilling and filling of the voids produced. And the firm created new markets in countries where no diamond tradition had existed before.
Ayer's marketing included product placement , advertising focused on the diamond product itself rather than the De Beers brand, and associations with celebrities and royalty.
Without advertising the De Beers brand, De Beers was advertising its competitors' diamond products as well,  but this was not a concern as De Beers dominated the diamond market throughout the 20th century.
De Beers still advertises diamonds, but the advertising now mostly promotes its own brands, or licensed product lines, rather than completely "generic" diamond products.
Brown-colored diamonds constituted a significant part of the diamond production, and were predominantly used for industrial purposes. They were seen as worthless for jewelry not even being assessed on the diamond color scale.
After the development of Argyle diamond mine in Australia in , and marketing, brown diamonds have become acceptable gems.
Industrial diamonds are valued mostly for their hardness and thermal conductivity, making many of the gemological characteristics of diamonds, such as the 4 Cs , irrelevant for most applications.
The boundary between gem-quality diamonds and industrial diamonds is poorly defined and partly depends on market conditions for example, if demand for polished diamonds is high, some lower-grade stones will be polished into low-quality or small gemstones rather than being sold for industrial use.
Within the category of industrial diamonds, there is a sub-category comprising the lowest-quality, mostly opaque stones, which are known as bort.
Industrial use of diamonds has historically been associated with their hardness, which makes diamond the ideal material for cutting and grinding tools.
As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds.
Common industrial applications of this property include diamond-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.
Specialized applications include use in laboratories as containment for high-pressure experiments see diamond anvil cell , high-performance bearings , and limited use in specialized windows.
The high thermal conductivity of diamond makes it suitable as a heat sink for integrated circuits in electronics.
The mining and distribution of natural diamonds are subjects of frequent controversy such as concerns over the sale of blood diamonds or conflict diamonds by African paramilitary groups.
Only a very small fraction of the diamond ore consists of actual diamonds. The ore is crushed, during which care is required not to destroy larger diamonds, and then sorted by density.
Today, diamonds are located in the diamond-rich density fraction with the help of X-ray fluorescence , after which the final sorting steps are done by hand.
Before the use of X-rays became commonplace,  the separation was done with grease belts; diamonds have a stronger tendency to stick to grease than the other minerals in the ore.
Historically, diamonds were found only in alluvial deposits in Guntur and Krishna district of the Krishna River delta in Southern India. Diamond extraction from primary deposits kimberlites and lamproites started in the s after the discovery of the Diamond Fields in South Africa.
Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia. In the U. The Crater of Diamonds State Park in Arkansas is open to the public, and is the only mine in the world where members of the public can dig for diamonds.
In some of the more politically unstable central African and west African countries, revolutionary groups have taken control of diamond mines , using proceeds from diamond sales to finance their operations.
Diamonds sold through this process are known as conflict diamonds or blood diamonds. In response to public concerns that their diamond purchases were contributing to war and human rights abuses in central and western Africa, the United Nations , the diamond industry and diamond-trading nations introduced the Kimberley Process in This is done by requiring diamond-producing countries to provide proof that the money they make from selling the diamonds is not used to fund criminal or revolutionary activities.
Although the Kimberley Process has been moderately successful in limiting the number of conflict diamonds entering the market, some still find their way in.
This is a stringent tracking system of diamonds and helps protect the "conflict free" label of Canadian diamonds. Synthetic diamonds are diamonds manufactured in a laboratory, as opposed to diamonds mined from the Earth.
The gemological and industrial 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 a century.
However, in recent years it has become possible to produce gem-quality synthetic diamonds of significant size. The majority of commercially available synthetic diamonds are yellow and are produced by so-called high-pressure high-temperature HPHT processes.
Other colors may also be reproduced such as blue, green or pink, which are a result of the addition of boron or from irradiation after synthesis.
Another popular method of growing synthetic diamond is chemical vapor deposition CVD. The growth occurs under low pressure below atmospheric pressure.
It involves feeding a mixture of gases typically 1 to 99 methane to hydrogen into a chamber and splitting them to chemically active radicals in a plasma ignited by microwaves , hot filament , arc discharge , welding torch or laser.
A diamond simulant is a non-diamond material that is used to simulate the appearance of a diamond, and may be referred to as diamante.
Cubic zirconia is the most common. The gemstone moissanite silicon carbide can be treated as a diamond simulant, though more costly to produce than cubic zirconia.
Both are produced synthetically. Diamond enhancements are specific treatments performed on natural or synthetic diamonds usually those already cut and polished into a gem , which are designed to better the gemological characteristics of the stone in one or more ways.
These include laser drilling to remove inclusions, application of sealants to fill cracks, treatments to improve a white diamond's color grade, and treatments to give fancy color to a white diamond.
Coatings are increasingly used to give a diamond simulant such as cubic zirconia a more "diamond-like" appearance. One such substance is diamond-like carbon —an amorphous carbonaceous material that has some physical properties similar to those of the diamond.
Advertising suggests that such a coating would transfer some of these diamond-like properties to the coated stone, hence enhancing the diamond simulant.
Techniques such as Raman spectroscopy should easily identify such a treatment. Early diamond identification tests included a scratch test relying on the superior hardness of diamond.
This test is destructive, as a diamond can scratch another diamond, and is rarely used nowadays. Instead, diamond identification relies on its superior thermal conductivity.
Electronic thermal probes are widely used in the gemological centers to separate diamonds from their imitations.
These probes consist of a pair of battery-powered thermistors mounted in a fine copper tip. One thermistor functions as a heating device while the other measures the temperature of the copper tip: if the stone being tested is a diamond, it will conduct the tip's thermal energy rapidly enough to produce a measurable temperature drop.
This test takes about two to three seconds. Whereas the thermal probe can separate diamonds from most of their simulants, distinguishing between various types of diamond, for example synthetic or natural, irradiated or non-irradiated, etc.
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 synthetic diamonds. They can also identify the vast majority of treated natural diamonds.
Laboratories use techniques such as spectroscopy, microscopy and luminescence under shortwave ultraviolet light to determine a diamond's origin.
Several methods for identifying synthetic diamonds can be performed, depending on the method of production and the color of the diamond.
CVD diamonds can usually be identified by an orange fluorescence. Screening devices based on diamond type detection can be used to make a distinction between diamonds that are certainly natural and diamonds that are potentially synthetic.
Those potentially synthetic diamonds require more investigation in a specialized lab. Occasionally, large thefts of diamonds take place.
The gang broke through a perimeter fence and raided the cargo hold of a Swiss-bound plane. The gang have since been arrested and large amounts of cash and diamonds recovered.
The identification of stolen diamonds presents a set of difficult problems. Rough diamonds will have a distinctive shape depending on whether their source is a mine or from an alluvial environment such as a beach or river—alluvial diamonds have smoother surfaces than those that have been mined.
Determining the provenance of cut and polished stones is much more complex. The Kimberley Process was developed to monitor the trade in rough diamonds and prevent their being used to fund violence.
Before exporting, rough diamonds are certificated by the government of the country of origin. Some countries, such as Venezuela, are not party to the agreement.
The Kimberley Process does not apply to local sales of rough diamonds within a country. Diamonds may be etched by laser with marks invisible to the naked eye.
Lazare Kaplan , a US-based company, developed this method. However, whatever is marked on a diamond can readily be removed.
Diamonds have been treasured as gemstones since their use as religious icons in ancient India. Their usage in engraving tools also dates to early human history.
In , the French scientist Antoine Lavoisier used a lens to concentrate the rays of the sun on a diamond in an atmosphere of oxygen , and showed that the only product of the combustion was carbon dioxide , proving that diamond is composed of carbon.
From Wikipedia, the free encyclopedia. This article is about the mineral. For the gemstone, see Diamond gemstone. Allotrope of carbon often used as a gemstone and an abrasive.
It is however highly doubtful that Pliny meant diamonds, and it is assumed that in fact several minerals such as corundum , spinel , or even a mixture with magnetite were all referred to by the word "adamas".
Diamonds eventually spread throughout the world, even though India had remained the only major source of the gemstone until diamonds were discovered in Brazil in The modern era of diamond mining began in the s in Kimberley , South Africa with the opening of the first large-scale diamond mine.
In , an even larger This sparked off the famous "New Rush" and within a month, claims were cut into the hillock which were worked frenetically by two to three thousand men.
As the land was lowered so the hillock became a mine—in time, the world-renowned Kimberley Mine. In , the two companies merged to form De Beers Consolidated Mines , which once had a monopoly over the world's diamond market.
The diamond cutters of Antwerp are world renowned for their skill. More than 12, expert cutters and polishers are at work in the Diamond District , at workshops, serving 1, firms and 3, brokers and merchants.
In the 21st century, the technology to produce perfect diamonds synthetically was developed. Diamonds produced by the latest technologies are visually identical to mined, naturally occurring diamonds.
It is too early to assess the effect of future wide availability of gem-quality synthetic diamonds on the diamond market, although the traditional diamond industry has taken steps to try to create a distinction between diamonds dug from the ground and diamonds made in a factory, in part by downplaying the fact that diamonds from both sources are actually visually identical.
The most familiar usage of diamonds today is as gemstones used for adornment —a usage which dates back into antiquity. The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds.
In the twentieth century, gemologists have developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem.
Four characteristics known informally as the "four Cs" are now commonly used as the basic descriptors of diamonds: carat, cut, color, and clarity.
This system was developed by Gemological Institute of America in as internationally recognized standard to evaluate diamonds characteristics.
Most gem diamonds are traded on the wholesale market based on single values for each of the four Cs; for example knowing that a diamond is rated as 1.
More detailed information from within each characteristic is used to determine actual market value for individual stones. Consumers who purchase individual diamonds are often advised to use the four Cs to pick the diamond that is "right" for them.
Other characteristics also influence the value and appearance of a gem diamond. These include physical characteristics such as the presence of fluorescence as well as the diamond's source and which gemological institute evaluated the diamond.
Cleanliness also dramatically affects a diamond's beauty. There are two major non-profit gemological associations which grade and provide reports, informally referred to by the term certificate or cert , which is a misnomer for many grading reports on diamonds; while carat weight and cut angles are mathematically defined, the clarity and color are judged by the trained human eye and are therefore open to slight variance in interpretation.
These associations are listed below. Within the last two decades, a number of for-profit gemological grading laboratories have also been established, many of them also based in Antwerp or New York.
These entities serve to provide similar services as the non-profit associations above, but in a less expensive and more timely fashion. They produce certificates that are similar to those of the GIA.
The carat weight measures the mass of a diamond. One carat is defined as milligrams about 0. The point unit—equal to one one-hundredth of a carat 0.
All else being equal, the price per carat increases with carat weight, since larger diamonds are both rarer and more desirable for use as gemstones.
The price per carat does not increase linearly with increasing size. Instead, there are sharp jumps around milestone carat weights, as demand is much higher for diamonds weighing just more than a milestone than for those weighing just less.
As an example, a 0. Jewelers often trade diamonds at negotiated discounts off the Rapaport price e.
In the wholesale trade of gem diamonds, carat is often used in denominating lots of diamonds for sale. Because of this, diamond prices particularly among wholesalers and other industry professionals are often quoted per carat, rather than per stone.
Total carat weight t. Diamond solitaire earrings, for example, are usually quoted in t. Clarity is a measure of internal defects of a diamond called inclusions.
Inclusions may be crystals of a foreign material or another diamond crystal, or structural imperfections such as tiny cracks that can appear whitish or cloudy.
The number, size, color, relative location, orientation, and visibility of inclusions can all affect the relative clarity of a diamond.
Diamonds become increasingly rare when considering higher clarity gradings. Those that do not have a visible inclusion are known as "eye-clean" and are preferred by most buyers, although visible inclusions can sometimes be hidden under the setting in a piece of jewelry.
Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity. When set in jewelry, it may also be possible to hide certain inclusion behind mounting hardware such as prongs in a way that renders the defect invisible.
However, large clouds can affect a diamond's ability to transmit and scatter light. Large cracks close to or breaking the surface may increase the likelihood of a fracture.
The finest quality as per color grading is totally colorless, which is graded as D color diamond across the globe, meaning it is absolutely free from any color.
However, when studded in jewellery these very light colored diamonds do not show any color or it is not possible to make out color shades.
These are graded as E color or F color diamonds. Diamonds which show very little traces of color are graded as G or H color diamonds. Slightly colored diamonds are graded as I or J or K color.
A diamond can be found in any color in addition to colorless. Some of the colored diamonds, such as pink, are very rare.
A chemically pure and structurally perfect diamond is perfectly transparent with no hue , or color. However, in reality most gem-sized natural diamonds are imperfect.
Depending on the hue and intensity of a diamond's coloration, a diamond's color can either detract from or enhance its value.
For example, most white diamonds are discounted in price as a more yellow hue is detectable, while intense pink or blue diamonds such as the Hope Diamond can be dramatically more valuable.
The Aurora Diamond Collection displays a spectacular array of naturally colored diamonds , which occur in every color of the rainbow.
Most diamonds used as gemstones are basically transparent with little tint, or white diamonds. The most common impurity, nitrogen , replaces a small proportion of carbon atoms in a diamond's structure and causes a yellowish to brownish tint.
The GIA has developed a rating system for color in white diamonds, from D to Z with D being "colorless" and Z having a bright yellow coloration , which has been widely adopted in the industry and is universally recognized, superseding several older systems.
The GIA system uses a benchmark set of natural diamonds of known color grade, along with standardized and carefully controlled lighting conditions.
Diamonds with higher color grades are rarer, in higher demand, and therefore more expensive, than lower color grades. Oddly enough, diamonds graded Z are also rare, and the bright yellow color is also highly valued.
N—Y usually appear light yellow or brown. In contrast to yellow or brown hues, diamonds of other colors are more rare and valuable.
While even a pale pink or blue hue may increase the value of a diamond, more intense coloration is usually considered more desirable and commands the highest prices.
A variety of impurities and structural imperfections cause different colors in diamonds, including yellow, pink, blue, red, green, brown, and other hues.
Black diamond's natural form is known as Carbonado , the toughest form of the diamond which is porous and difficult to cut. Black diamonds are natural, man-made, treated black diamonds.
Some black diamonds are expensive than other types of black diamonds because of the quality, durability, production cost, and few other factors.
Intense yellow coloration is considered one of the fancy colors, and is separate from the color grades of white diamonds. Gemologists have developed rating systems for fancy colored diamonds, but they are not in common use because of the relative rarity of such diamonds.
Diamond cutting is the art and science of creating a gem-quality diamond out of mined rough. The cut of a diamond describes the manner in which a diamond has been shaped and polished from its beginning form as a rough stone to its final gem proportions.
The cut of a diamond describes the quality of workmanship and the angles to which a diamond is cut. Often diamond cut is confused with "shape". There are mathematical guidelines for the angles and length ratios at which the diamond is supposed to be cut in order to reflect the maximum amount of light.
Round brilliant diamonds, the most common, are guided by these specific guidelines, though fancy cut stones are not able to be as accurately guided by mathematical specifics.
The techniques for cutting diamonds have been developed over hundreds of years, with perhaps the greatest achievements made in by mathematician and gem enthusiast Marcel Tolkowsky.
He developed the round brilliant cut by calculating the ideal shape to return and scatter light when a diamond is viewed from above.
The modern round brilliant has 57 facets polished faces , counting 33 on the crown the top half , and 24 on the pavilion the lower half.
The girdle is the thin middle part. The function of the crown is to refract light into various colors and the pavilion's function to reflect light back through the top of the diamond.
The culet is the tiny point or facet at the bottom of the diamond. This should be a negligible diameter, otherwise light leaks out of the bottom. Tolkowsky's calculations included neither a culet nor a girdle.
However, a girdle is required in reality in order to prevent the diamond from easily chipping in the setting. The thick part of the girdle is normally about 1.
The further the diamond's characteristics are from the Tolkowsky's ideal, the less light will be reflected. However, there is a small range in which the diamond can be considered "ideal".
Tolkowsky's calculations can be repeated for a narrow range of pavilion angles. Such calculations show a slightly larger table percentage, and a trade-off between pavilion angle and crown angle.
Today, because of the relative importance of carat weight among buyers, many diamonds are often intentionally cut poorly to increase carat weight.
There is a financial premium for a diamond that weighs the desirable 1. Neither of these changes makes the diamond appear any larger, and both greatly reduce the sparkle of the diamond.
A poorly cut 1. The depth percentage is the overall quickest indication of the quality of the cut of a round brilliant. Another quick indication is the overall diameter.
Most industrial diamonds are gray or brown and are translucent or opaque, but better-quality industrial stones grade imperceptibly into poor quality gems.
The colour of diamonds may be changed by exposure to intense radiation as released in a nuclear reactor or by a particle accelerator or by heat treatment.
A very high refractive power gives the diamond its extraordinary brilliance. A properly cut diamond will return a greater amount of light to the eye of the observer than will a gem of lesser refractive power and will thus appear more brilliant.
The high dispersion gives diamonds their fire, which is caused by the separation of white light into the colours of the spectrum as it passes through the stone.
The scratch hardness of diamond is assigned the value of 10 on the Mohs scale of hardness ; corundum, the mineral next to diamond in hardness, is rated as 9.
The hardness of a diamond varies significantly in different directions, causing cutting and polishing of some faces to be easier than others.
For detailed physical properties, see native element table. In the atomic structure of diamond, as determined by X-ray diffraction techniques, each carbon atom is linked to four equidistant neighbours throughout the crystal.
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Britannica Quiz.Diamonds can scratch other diamonds, but this can result in damage Tallinn Kommende Veranstaltungen one or both stones. Archived from the original Spielebar March 17, If they are visible in outcrops, the Diamonds are never visible because they are so rare. They weather quickly within a few years after exposure and tend to have lower topographic relief than surrounding rock. Of all known substances, it is the hardest and least compressible. This test is destructive, as a diamond can scratch another diamond, and is rarely used nowadays. Diamond has a cleavage plane and is therefore more fragile in some orientations than others. Archived from the original on July 16, Beste Spielothek in Hinterkreith finden