Diamond enhancement

Diamond enhancements are specific treatments, performed on natural diamonds (usually those already cut and polished into gems), which are designed to improve the gemological characteristics — and therefore the value — of the stone in one or more ways. These include clarity treatments such as laser drilling to remove inclusions, application of sealants to fill cracks, color treatments to improve a white diamond's color grade, and treatments to give fancy color to a white or off-color diamond.

The CIBJO and government agencies such as the United States Federal Trade Commission explicitly require the disclosure of most diamond treatments at the time of sale. Some treatments, particularly those applied to clarity, remain highly controversial within the industry — this arises from the traditional notion that diamond holds a unique or "sacred" place among the gemstones, and should not be treated too radically, if for no other reason than a fear of damaging consumer confidence.

Treated diamonds usually trade at a significant discount to untreated diamonds. This is due to several factors, including relative scarcity — a much larger number of stones can be treated to reach gem quality than are found naturally occurring in a gem quality state — and the potential impermanence of various treatments. Therefore, it is unusual to see a diamond with good overall gemological characteristics undergo treatment. Diamonds which are chosen for treatment are usually those that would be otherwise difficult to sell as gem diamonds, where inclusions or fractures noticeably detract from the beauty of the diamond to even casual observers. In these cases, the loss in value due to treating the diamond is more than overcome by the value added by mitigating obvious flaws.

Distribution

The Diamond Trading Company (DTC) is a subsidiary of De Beers and markets rough diamonds from De Beers-operated mines (it withdrew from purchasing diamonds on the open market in 1999 and ceased purchasing Russian diamonds mined by Russian company Alrosa, at the end of 2008. Alrosa has successfully appealed against a European court ruling[64] and will resume is sales in May 2009.[65]).

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. The cutting and polishing of rough diamonds is a specialized skill that is concentrated in a limited number of locations worldwide. Traditional diamond cutting centers are Antwerp, Amsterdam, Johannesburg, New York, and Tel Aviv. Recently, diamond cutting centers have been established in China, India, Thailand, Namibia and Botswana. Cutting centers with lower cost of labor, notably Surat in Gujarat, India, handle a larger number of smaller carat diamonds, while smaller quantities of larger or more valuable diamonds are more likely to be handled in Europe or North America. 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.[40]

Diamonds which have been prepared as gemstones are sold on diamond exchanges called bourses. There are 26 registered diamond bourses in the world.[66] 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 which they 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 were valued at US$9 billion as rough diamonds, US$14 billion after being cut and polished, US$28 billion in wholesale diamond jewelry, and US$57 billion in retail sales.[67]

Supply chain

Approximately 130 million carats (26,000 kg (57,000 lb)) are mined annually, with a total value of nearly USD $9 billion, and about 100,000 kg (220,000 lb) are synthesized annually.[49]

Roughly 49% of diamonds originate from central and southern Africa, although significant sources of the mineral have been discovered in Canada, India, Russia, Brazil, and Australia. They are mined from kimberlite and lamproite 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 are subjects of frequent controversy such as with concerns over the sale of conflict diamonds or blood diamonds by African paramilitary groups.[50] The diamond supply chain is controlled by a limited number of powerful businesses, and is also highly concentrated in a small number of locations around the world

Light performance

In the gem trade the term light performance is used to describe how well a polished diamond will return light to the viewer. There are three light properties which are described in relation to light performance; brilliance, fire, and scintillation. Brilliance refers to the white light reflections from the external and internal facet surfaces. Fire refers to the spectral colors which are produced as a result of the diamond dispersing the white light. Scintillation refers to the small flashes of light that are seen when the diamond, light source or the viewer is moved. A diamond that is cut and polished to produce a high level of these qualities is said to be high in light performance.

The setting diamonds are placed in also affect the performance of light through a diamond. The 3 most commonly used settings are: Prong, Bezel, and Channel. Prong settings are the most popular setting for diamond jewelry. The prong setting consists of four or six 'claws' that cradle the diamond, allowing the maximum amount of light to enter from all angles, allowing the diamonds to appear larger and more brilliant. In bezel settings the diamond or gemstone is completely surrounded by a rim of metal, which can be molded into any shape to accommodate the stone. Used to set earrings, necklaces, bracelets, and rings, bezel settings can have open or closed backs, and generally can be molded to allow a lot of light to pass through. Channel settings set the stones right next to each other with no metal separating them. This setting is mostly used in wedding and anniversary bands. The outer ridge is then worked over the edges of the stones to create a smooth exterior surface. This also protects the girdle area of the stone.

Diamond Cut

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 1919 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 diffuse light into various colors and the pavilion's function to reflect light back through the top of the diamond.

Tolkowsky defined the ideal dimensions as:

Table percentage (table diameter divided by overall diameter) = 53%
Depth percentage (Overall depth divided by the overall diameter) = 59.3%
Pavilion Angle (Angle between the girdle and the pavilion) = 40.75°
Crown Angle (Angle between the girdle and the crown) = 34.5°
Pavilion Depth (Depth of pavilion divided by overall diameter) = 43.1%
Crown Depth (Depth of crown divided by crown diameter) = 16.2%
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 ideal dimensions did not include a culet. However, a thin culet is required in reality in order to prevent the diamond from easily chipping in the setting. A normal culet should be about 1%–2% of the overall diameter.

The further the diamond's characteristics are from Tolkowsky's ideal, the less light will be reflected. However, there is a small range in which the diamond can be considered "ideal." Today, because of the relative importance of carat weight in society, many diamonds are often intentionally cut poorly to increase carat weight. There is a financial premium for a diamond that weighs the magical 1.0 carat (200 mg), so often the girdle is made thicker or the depth is increased. Neither of these tactics make the diamond appear any larger, and both greatly reduce the sparkle of the diamond. So a poorly cut 1.0 carat (200 mg) diamond may have the same diameter and appear as large as a 0.85 carats (170 mg) diamond. The depth percentage is the overall quickest indication of the quality of the cut of a round brilliant. "Ideal" round brilliant diamonds should not have a depth percentage greater than 62.5%. Another quick indication is the overall diameter. Typically a round brilliant 1.0 carat (200 mg) diamond should have a diameter of about 6.5 mm. Mathematically, the diameter in millimeters of a round brilliant should approximately equal 6.5 times the cube root of carat weight, or 11.1 times the cube root of gram weight, or 1.4 times the cube root of point weight.

Ideal cuts can be controversial as the definitions of brilliance and beauty are very subjective.

Tolkowsky's mathematical model is now superseded by the GIA Facetware software that is the culmination of 20 years of studies on diamond cuts.

New diamond cuts are now all the rage in the diamond industry as for example a design invented in 2003 and called the Genesis cut. This cut differs in shape from the more traditional cuts in its concave surfaces and angles and resembles a 4-pointed star.

Symbolism and Lore

Historically, it has been claimed that diamonds possess several supernatural powers:

A diamond gives victory to he or she who carries it bound on his left arm, no matter the number of enemies.[12]
Panics, pestilences, enchantments, all fly before it; hence, it is good for sleepwalkers and the insane.[12]
It deprives lodestone and magnets of their virtue (i.e., ability to attract iron).[12]
Arabic diamonds are said to attract iron greater than a magnet.[12]
A diamond's hardiness can only be broken by smearing it with fresh goat's blood.[12]
In traditional Hinduism one should avoid contact with a diamond which surface area is damaged by a crack, a crowfoot, round, dull, speckled area or which is black-blue, flat, and if uncut, other than the (ideal) hexagonal shape.[13]
Because of their extraordinary physical properties, diamonds have been used symbolically since near the time of their first discovery. Perhaps the earliest symbolic use of diamonds was as the eyes of Hindu devotional statues.[14] In Hinduism Indra uses Vajrayudham or the thunderbolt as his primary weapon. Vajra is the word for diamond and ayudham means weapon in Sanskrit. Another name for it was Agira which means fire or the sun. In fact there are 14 names counted to be given to a diamond in traditional Hinduism.[13]

The oldest dated printed book in the world is called the Diamond Sutra, a Chinese text dates from AD 868 and was found in the Mogao Caves. Sutras are most used to describe the teachings of Buddha. In this case the title of the Sutra refers not to the diamond itself but to a 'diamond blade that will cut through worldly illusion to illuminate what is real and everlasting'. Jewel imagery forms a central part of Buddhism: the triple-jewel represents 'Buddha', his teachings 'Dharma' and the spiritual community 'Shangha'. The book presently resides in the British Library.[15]

Many cultures use divine intervention to explain the origin and creation of gemstones, and diamonds were no exception to this. In Greek mythology for example it was the youth on the island of Crete that disturbed Zeus and who were then (as a form of punishment) transformed into the adamas.[16]

Philosophers however had a more naturalistic approach to explain the origin of gems: Plato for example believed gemstones were a consequence of fermentation in the stars, where a diamond actually formed the kernel of gold-bearing mass.[16] In fact often diamonds were linked to gold, which may have found its origin in the joint occurrence of diamonds with quartzite, quartz veins and an occasional occurrence of gold in them.[17]

In later times, Robert Boyle actually believed that gems (including a diamond) were formed of clear, transparent water, and that their colors and characteristics were derived from their metallic spirit.[18]

The diamond is the birthstone for people born in the month of April, and is also used as the symbol of a sixty-year anniversary, such as a Diamond Jubilee (see hierarchy of precious substances). In a system of heraldry by gemstone occasionally used in the past for the arms of nobles, diamond was used to represent the color sable, or black.[19]

Blood 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. Major diamond trading corporations continue to fund and fuel these conflicts by doing business with armed groups. In response to public concerns that their diamond purchases were contributing to war and human rights abuses in central Africa and West Africa, the United Nations, the diamond industry and diamond-trading nations introduced the Kimberley Process in 2002, which is aimed at ensuring that conflict diamonds do not become intermixed with the diamonds not controlled by such rebel groups, by providing documentation and certification of diamond exports from producing countries to ensure that the proceeds of sale are not being 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, conflict diamonds smuggled to market continue to persist to some degree (approx. 2–3% of diamonds traded today are possible conflict diamonds[23]). According to the 2006 book The Heartless Stone, two major flaws still hinder the effectiveness of the Kimberley Process: the relative ease of smuggling diamonds across African borders and giving phony histories, and the violent nature of diamond mining in nations that are not in a technical state of war and whose diamonds are therefore considered "clean."[24]

The Canadian Government has set up a body known as Canadian Diamond Code of Conduct[25] to help authenticate Canadian diamonds. This is a very stringent tracking system of diamonds and helps protect the 'conflict free' label of Canadian diamonds.

Currently, gem production totals nearly 30 million carats (6,000 kg) of cut and polished stones annually, and over 100 million carats (20,000 kg) of mined diamonds are sold for industrial use each year, as are about 100,000 kg of synthesized diamond.

The Ring

The origin of the custom to use diamonds in rings, and more recently, in engagement rings, can be traced back to the Middle Ages and even the Romans. The Romans valued the diamond entirely on account of the supernatural powers they ascribed to it. Pliny wrote that a diamond baffles poison, keeps off insanity, and dispels vain fears.[17] The medieval Italians copied these beliefs and added some to it: they called it the "Pietra della Reconciliazone" because it maintained concord between husband and wife. On this account it was recommended as the stone to be set in wedding (or espousal) rings—not on account of its beauty therefore, which was described by Isidore of Seville as a small stone devoid of beauty.[17]

In more recent times a Parisian Oracle of mystic subjects, the Baron d'Orchamps, announced the diamond, if worn on the left (hand) warded off evil influences and attracted good fortune and since he had fashionable clients the word spread and the wearing of the diamond on the left hand became in itself a fashion.[20]

One of the first occurrences of the diamond engagement (or wedding) ring can be traced back to the marriage of Maximilian I (then Archduke of Austria) to Mary of Burgundy in 1477.[21] Other early examples of betrothal jewels incorporating diamonds include the Bridal Crown of Blanche (ca. 1370–80)[21] and the Heftlein brooch of Vienna (ca. 1430–40),[21] a pictorial piece depicting a wedding couple.

The popularity of the diamond ring as an engagement ring for a much wider audience can be traced directly to the marketing campaigns of De Beers, starting in 1938.[22] Such a campaign had become necessary to sell the large quantity of diamonds suddenly available because of the large diamond finds particularly in South Africa.

In Western tradition, an engagement ring is a ring worn by a woman indicating her engagement to be married. Conventionally, the ring is presented as a betrothal gift by a man to his prospective bride while he proposes marriage or directly after she accepts his marriage proposal. It represents a formal agreement to future marriage.

In some countries, such as the United States and the United Kingdom, it is worn on the left-hand ring finger, while in other countries, such as Poland and Ukraine, it is customary for the ring to be worn on the right-hand. Similar traditions purportedly date to classical times, dating back from an early usage reportedly referring to the fourth finger of the left hand as containing the vena amoris or "vein of love".

In the United States and Canada today it is becoming more common, but still quite rare, that a woman will also buy her partner an engagement ring (also called a pre-engagement ring, promise ring, or 'mangagement' ring) at the time of the engagement.[1]

Shape of Diamonds

Diamonds do not show all of their beauty as rough stones; instead, they must be cut and polished to exhibit the characteristic fire and brilliance that diamond gemstones are known for. Diamonds are cut into a variety of shapes that are generally designed to accentuate these features.

Diamonds which are not cut into a round brilliant shape are known as "fancy cuts." Popular fancy cuts include the baguette (from the French, meaning rod or loaf of bread), marquise, princess cut (square outline), heart, briolette (a form of the rose cut), and pear cuts. Newer cuts that have been introduced into the jewelry industry are the "cushion" "radiant" (similar to princess cuts, but with rounded edges instead of square edges) and Asscher cuts. Many fancy colored diamonds are now being cut according to these new styles. Generally speaking, these "fancy cuts" are not held to the same strict standards as Tolkowsky-derived round brilliants and there are less specific mathematical guidelines of angles which determine a well-cut stone. Cuts are influenced heavily by fashion: the baguette cut—which accentuates a diamond's luster and downplays its fire—was all the rage during the Art Deco period, whereas the princess cut —which accentuates a diamond's fire rather than its luster—is currently gaining popularity. The princess cut is also popular amongst diamond cutters: of all the cuts, it wastes the least of the original crystal. The past decades have seen the development of new diamond cuts, often based on a modification of an existing cut. Some of these include extra facets. These newly developed cuts are viewed by many as more of an attempt at brand differentiation by diamond sellers, than actual improvements to the state of the art.

Diamond clarity

Diamond clarity is a quality of diamonds relating to the existence and visual appearance of internal characteristics of a diamond called inclusions, and surface defects called blemishes. Clarity is one of the four Cs of diamond grading, the others being carat, color, and cut. 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. A clarity grade is assigned based on the overall appearance of the stone under 10x magnification.

Most inclusions present in gem-quality diamonds do not affect the diamonds' performance or structural integrity. However, large clouds can affect a diamond's ability to transmit and scatter light. Large cracks close to or breaking the surface may reduce a diamond's resistance to fracture.

Diamonds with higher clarity grades are more valued, with the exceedingly rare "flawless" graded diamond fetching the highest price. Minor inclusions or blemishes are useful, as they can be used as unique identifying marks analogous to fingerprints. In addition, as synthetic diamond technology improves and distinguishing between natural and synthetic diamonds becomes more difficult, inclusions or blemishes can be used as proof of natural origin.

Chemical vapor deposition of diamond

Chemical vapor deposition of diamond is a method of producing synthetic diamond by creating the circumstances necessary for carbon atoms in a gas to settle on a substrate in crystalline form.

Chemical vapor deposition of diamond has received a great deal of attention in the materials sciences because it allows many new applications of diamond that had previously been either too expensive to implement or too difficult to make economical. CVD diamond growth typically occurs under low pressure (1-27 kPa; 0.145-3.926 psi; 7.5-203 Torr) and involves feeding varying amounts of gases into a chamber, energizing them and providing conditions for diamond growth on the substrate. The gases always include a carbon source, and typically include hydrogen as well, though the amounts used vary greatly depending on the type of diamond being grown. Energy sources include hot filament, microwave power, and arc discharges, among others. The energy source is intended to generate a plasma in which the gases are broken down and more complex chemistries occur. The actual chemical process for diamond growth is still under study and is complicated by the very wide variety of diamond growth processes used.

The advantages to CVD diamond growth include the ability to grow diamond over large areas, the ability to grow diamond on a substrate, and the control over the properties of the diamond produced. In the past, when high pressure high temperature (HPHT) techniques were used to produce diamond, the diamonds were typically very small free standing diamonds of varying sizes. With CVD diamond growth areas of greater than fifteen centimeters (six inches) diameter have been achieved and much larger areas are likely to be successfully coated with diamond in the future. Improving this ability is key to enabling several important applications.

The ability to grow diamond directly on a substrate is important because it allows the addition of many of diamond’s important qualities to other materials. Since diamond has the highest thermal conductivity of any material, layering diamond onto high heat producing electronics (such as optics and transistors) allows the diamond to be used as a heat sink[1][2]. Diamond films are being grown on valve rings, cutting tools, and other objects that benefit from diamond’s hardness and exceedingly low wear rate. In each case the diamond growth must be carefully done to achieve the necessary adhesion onto the substrate. Diamond's very high scratch resistance and thermal conductivity, combined with a lower coefficient of thermal expansion than Pyrex glass, a coefficient of friction close to that of Teflon (Polytetrafluoroethylene) and strong lipophilicity would make it a nearly ideal non-stick coating for cookware if large substrate areas could be coated economically.

The most important attribute of CVD diamond growth is the ability to control the properties of the diamond produced. In the area of diamond growth the word “diamond” is used as a description of any material primarily made up of sp3 bonded carbon, and there are many different types of diamond included in this. By regulating the processing parameters—especially the gases introduced, but also including the pressure the system is operated under, the temperature of the diamond, and the method of generating plasma—many different materials that can be considered diamond can be made. Single crystal diamond can be made containing various dopants[3]. Polycrystalline diamond consisting of grain sizes from several nanometers to several micrometers can be grown[4][5]. Some polycrystalline diamond grains are surrounded by thin, non-diamond carbon, while others are not. These different factors affect the diamond’s hardness, smoothness, conductivity, optical properties and more.

List of diamonds

A number of large or extraordinary diamonds have gained fame, both as exquisite examples of the beautiful nature of diamonds, and because of the famous people who wore, bought, and sold them. These diamonds are often depicted in marketing materials aimed at the retail diamond customer. A partial list of famous diamonds in history follows.





Darya-ye Noor
Tiffany Yellow DiamondThe Akbar Shah, an Indian diamond with a roughly pear-shaped outline and random faceting, including two Arabic inscriptions, the first reading "Shah Akbar, the Shah of the World, 1028 A.H." (the letters mean "After Hegira", the first year of the Muslim era, A.D. 622. The second inscription read "To the Lord of Two Worlds, 1039 A.H. Shah Jehan". The diamond was reportedly part of the original Peacock Throne. Purchased in 1886 in Constantinople by London merchant George Blogg, who recut it from 116 carats to a pear-shape of 71.70 carats, thus destroying the historic inscriptions. Blogg was the last known owner and the stone's whereabouts are presently unknown.
The Allnatt Diamond, a large antique cushion-shaped brilliant Fancy Vivid Yellow diamond.
The Agra Diamond, antique cushion-shaped stellar brilliant, 28 carats.
The Amsterdam Diamond, a 33.74 carat (6.748 g) pear-shaped black diamond which sold for $352,000 in 2001.
The Archduke Joseph Diamond, antique cushion-shaped brilliant, originally weighing 78.54 carats, purchased by Molina Jewelers of Arizona sometime in the late-1990s and slightly recut to 76.45 carats to improve clarity and symmetry. D color, Internally Flawless.
The Ashberg Diamond
The Aurora Butterfly of Peace
The Aurora Pyramid of Hope
The Beau Sancy, a 34-carat diamond not to be confused with the Sancy.
The Black Orlov, a 67.50 carat cushion-cut black diamond, also called the Eye of Brahma Diamond.
The Blue Heart Diamond, 30.82-carat heart brilliant. Part of the Smithsonian collection.
The Briolette of India Diamond, 90 carats.
The Centenary Diamond, modified heart-shaped brilliant, the world's largest colorless (grade D), flawless diamond.
The Chloe Diamond, largest round brilliant-cut diamond ever put on auction. Sold on November 14th, 2007 at Sotheby's in Geneva to Georges Marciano of the Guess clothing line for $16.2 million, the second-highest price ever paid for a diamond on auction. Took 2 years to cut.
The Cross of Asia, discovered in 1902 in South Africa as a 280-carat crystal. At first diamond was cut to 142 carats, and next the cut was three times changed to 112 carats, a cushion-cut of 109.28 carats (the weight Lawrence Copeland's "Diamonds - Famous, Notable and Unique" lists it at) measuring 1⅛ × ⅞ × ⅝ inches, and finally into a radiant-cut gem of 79.12 carats to elimination all flaws. It is Fancy Yellow and Internally Flawless.[1]
The Cullinan Diamond, the largest rough gem-quality diamond ever found at 3106.75 carats (621.35 g). It was cut into 105 diamonds including the Cullinan I or the Great Star of Africa, 530.2 carats (106.04 g), and the Cullinan II or the Lesser Star of Africa, 317.4 carats (63.48 g), both of which are now part of the British Crown Jewels.
The Darya-ye Noor Diamond, the largest pink diamond in the world, about 186 carats (36.4 g), part of Iranian Crown Jewels. Its exact weight isn't known and 186 carats is an estimate.
The Deepdene, widely considered to be the largest artificially irradiated diamond in the world.
The De Young Red Diamond, the third-largest known red diamond was bought in a flea market on a hatpin by Sidney deYoung a prominent Boston estate jewelry merchant. It was donated by him to the museum of natural history.
The Dresden Green Diamond, antique pear-shaped brilliant - its color is the result of natural irradiation
The Dresden White Diamond, 47-carat antique oval brilliant, colorless/near-colorless
The Dresden Yellow Diamond, an antique round cut weighing 38 carats
The Earth Star Diamond a 111.59-carat, pear-shaped diamond with a strong coffee-like brown color.
The Empress Eugenie Diamond, 52-carat antique pear-shaped brilliant with an odd, random facet pattern
The Excelsior Diamond, the largest known diamond in the world prior to the Cullinan
The Florentine Diamond, a lost diamond, light yellow with a weight of 137.27 carats (27.45 g).
The Golden Eye Diamond, a world's largest, flawless, 'perfect-cut' Canary Yellow diamond (43.5 carats).
The Golden Jubilee Diamond, the largest faceted diamond ever cut at 545.67 carats (109.13 g)
The Graff Blue Diamond
The Great Chrysanthemum Diamond
The Great Mogul Diamond, fabled 280-carat mogul-cut diamond, now lost, although presumed by historians to have been recut as the Orlov.
The Gruosi Diamond, a heart-shaped black diamond, weighing 115.34 carats.
The Heart of Eternity Diamond, perhaps the largest Fancy Vivid Blue
The Hope Diamond, Fancy Dark Grayish-Blue and supposedly cursed. Almost certainly cut from the French Blue Diamond
The Hortensia Diamond, peach color, formerly part of the French Crown Jewels. Displayed in the Louvre.
The Idol's Eye
The Incomparable Diamond, a brownish-yellow diamond of 407.48 carats (81.496 g) cut from an 890 carat (178 g) rough diamond of the same name - it appeared on eBay in 2002. Internally Flawless clarity.
The Jacob Diamond weighing 184.5 carats (36.90 g), also known as Imperial Diamond & Victoria Diamond.
The Jones Diamond
The Jubilee Diamond, originally known as the Reitz Diamond; perhaps the sixth-largest in the world.
The Kazanjian Red Diamond, a 5.05-carat Asscher-cut red diamond formerly known simply as "Red Diamond". It was cut from a 35-carat piece of boart discovered near Lichtenburg, South Africa. It reappeared in 2007 after a 37-year absence from sight, and was purchased by Kazanjian Brothers Inc.
The Kimberley Diamond
The Koh-i-Noor, a 105 carat (21.6 g) white of Indian origin, with a long and turbulent history and a good deal of legend surrounding it. After belonging to various Mughal and Persian rulers, it was taken away from the Maharaja Duleep Singh of Lahore and was presented to Queen Victoria during the British Raj, and is now part of the Crown of Queen Elizabeth the Queen Mother.
The Le luz de dia, a 201 carat (40.25 g) colorless diamond, with unknown history. The firs note about this gem is in a book from 16th century. Gem was sold for almost 24,5 million $ in 2004 and was stolen just couple days later. It hasn't appear since then.
The Lesotho
The Lesotho Promise, is the 15th-largest diamond, the tenth-largest white diamond, and the largest diamond to be found in 13 years
The Millennium Star, at 203 carats is the second-largest colorless (grade D), flawless diamond.

Koh-i-Noor (glass replica)The Moon of Baroda
The Moussaieff Red Diamond, the largest known Fancy Red
The Mouna Diamond, 112 carats, Fancy Intense Yellow cushion-shaped brilliant.
The Nassak Diamond[1]
The Nepal Diamond, fine quality antique pear-shaped brilliant, sold by Harry Winston to private collector in 1961. Thought to have originated from the Golconda Mines.
The Nizam Diamond
The Nur-Ul-Ain Diamond
The Ocean Dream Diamond, the only known natural Fancy Deep Blue-Green.
The Oppenheimer Diamond, one of the largest gem-quality uncut diamonds in the world.
The Orlov, an Indian mogul cut rumored to have served as the eye of a Hindu statue.
The Paragon Diamond
The Polar Star Diamond, a colorless cushion-shaped stellar brilliant diamond weighing 41.28 carats.
The Porter Rhodes Diamond, a colorless 53-carat Asscher-cut stone.
The Portuguese Diamond, 127-carat antique emerald cut with a pale yellow body color and very strong blue fluorescence. Part of the Smithsonian's collection.
The Premier Rose Diamond, 137.02-carat (27.4 g) stone cut from a 353.9-carat (70.8 g) rough gem of the same name
The Pumpkin Diamond, perhaps the largest Fancy Vivid Orange. 5.54 carats, modified cushion-shaped brilliant.
The Red Cross Diamond, 205 carats, yellow, cushion-shaped stellar brilliant cut.
The Regent Diamond, cushion-shaped stellar brilliant cut, formerly belonging to Louis XV, Louis XVI, and Napoleon Bonaparte, it now resides in the Louvre.
The Sancy, a shield-shaped pale yellow diamond currently in the Louvre.
The Shah Diamond, very old yellow diamond (found approximately in 1450 in India) currently housed in the Diamond Fund in Kremlin
The Spirit of de Grisogono Diamond, 312 carats, the world's largest cut black diamond.
The Spoonmaker's Diamond, circa 86-carat (17 g) diamond housed in Topkapı Palace in Istanbul.
The Star of Arkansas
The Star of the East, a 95-carat (19 g) stone once owned by Mrs. Evalyn McLean of Washington DC, who also owned the Hope Diamond.
The Star of Sierra Leone
The Star of South Africa, also known as the Dudley Diamond. This must not be confused with the Star of Africa. The Star of South Africa was the initial name given to this diamond, when it was purchased as an 83.5-carat rough diamond. The diamond is a D-color, pear-shaped stellar brilliant cut stone, weighing 47.69 carats.
The Star of the South
The Steinmetz Pink Diamond, modified oval brilliant cut (step cut crown, brilliant pavilion), largest known Fancy Vivid Pink.
The Taylor-Burton Diamond
The Tereschenko, 42-carat antique pear brilliant cut.
The Tiffany Yellow Diamond, antique modified cushion-shaped stellar brilliant cut, on display at Tiffany & Co.'s New York City store.
The Uncle Sam Diamond, the largest discovered in the US, emerald-cut, M color (pale brown), VVS2 clarity.
The Vargas
The Wittelsbach Diamond, 35.52 carats, Fancy Deep Grayish Blue, antique oval stellar brilliant cut. Sold at Christie's, London, December 10, 2008 for $23.4 million, currently the highest price ever paid for a diamond at auction.

Identification

It was stated that annealing can convert typically brown synthetically made (CVD) diamonds into colorless diamonds, and that after having sent these diamonds for diamond jewelry identification, they were not identified as different from natural diamonds.[73] Such claims are often made for new synthetics, simulants, and treated stones, so it is important to validate how the stones were submitted for identification.

Properly trained and equipped gemologists can distinguish between natural diamonds and synthetic diamonds. They can also identify the vast majority of treated natural diamonds, two exceptions being a small minority of HPHT-treated Type II diamonds and some artificially irradiated green diamonds. "Perfect" crystals (at the atomic lattice level) have never been found, so both natural and synthetic diamonds always possess characteristic imperfections, arising from the circumstances of their crystal growth, that allow them to be distinguished from each other.[74]

Laboratories use techniques such as spectroscopy, microscopy and luminescence under shortwave ultraviolet light to determine a diamond's origin. They also use specially made machines to aid them in the identification process. Two screening machines are the DiamondSure and the DiamondView, both produced by the DTC and marketed by the GIA.[75]

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. D-J colored diamonds can be screened through the Swiss Gemmological Institute's[76] Diamond Spotter. Stones in the D-Z color range can be examined through the DiamondSure UV/visible spectrometer, a tool developed by De Beers.[74] Similarly, natural diamonds usually have minor imperfections and flaws, such as inclusions of foreign material, that are not seen in synthetic diamonds.

Industrial Grade

The market for industrial-grade diamonds operates much differently from its gem-grade counterpart. Industrial diamonds are valued mostly for their hardness and heat conductivity, making many of the gemological characteristics of diamonds, such as clarity and color, irrelevant for most applications. This helps explain why 80% of mined diamonds (equal to about 135 million carats or 27 metric tons annually), unsuitable for use as gemstones, are destined for industrial use. In addition to mined diamonds, synthetic diamonds found industrial applications almost immediately after their invention in the 1950s; another 570 million carats (114 tons) of synthetic diamond is produced annually for industrial use. Approximately 90% of diamond grinding grit is currently of synthetic origin.[46]

The dominant industrial use of diamond is in cutting, drilling, grinding, and polishing. Most uses of diamonds in these technologies do not require large diamonds; in fact, most diamonds that are gem-quality except for their small size, can find an industrial use. Diamonds are embedded in drill tips or saw blades, or ground into a powder for use in grinding and polishing applications. 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.[47]

With the continuing advances being made in the production of synthetic diamonds, future applications are becoming feasible. Garnering much excitement is the possible use of diamond as a semiconductor suitable to build microchips from, or the use of diamond as a heat sink[48] in electronics.

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 suitable 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 or 'boart'.[47]