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The Cullinan Diamond, found by Frederick Wells, surface manager of the Premier Diamond Mining Company in Cullinan, Gauteng, South Africa, on January 26, 1905, is the largest rough gem-quality diamond ever found, at 3,106.75 carats (621.35 g). Although a carbonado found in Brazil weighed more than 3,600 carats (720 g), no gem-quality material could be extracted from it. The stone was named after Sir Thomas Cullinan, the owner of the diamond mine.
Sir William Crookes performed an analysis of the Cullinan diamond and mentioned among others its remarkable clarity but also a black spot in the middle. The colours around the black spot were very vivid and changed as the analyzer was turned. According to Crookes this pointed to severe internal strain. Such strains are not uncommon for diamonds, and have actually resulted in causing diamonds to explode when reaching the surface, or even in the pockets of the miners due to the exposure to the miner's body warmth.
The stone was bought by the Transvaal government [1] and presented to King Edward VII. It was cut into three large parts by Asscher Brothers of Amsterdam, and eventually into some 11 large gem-quality stones and a number of smaller fragments. At the time, technology had not yet evolved to guarantee quality of the modern standard, and cutting the diamond was considered difficult and risky. In order to enable Asscher to cut the diamond in one blow an incision was made, half an inch deep. Then a specifically designed knife was placed in the incision and the diamond was split in one heavy blow. The diamond split through a defective spot which was shared in both halves of the diamond.
"The tale is told of Joseph Asscher, the greatest cleaver of the day," wrote Michael Hart in his book Diamond: A Journey to the Heart of an Obsession, "that when he prepared to cleave the largest diamond ever known, the 3,160 carat (632 g) Cullinan, he had a doctor and nurse standing by and when he finally struck the diamond and it broke perfectly in two, he fainted dead away."
The largest polished gem from the stone is named Cullinan I or the Great Star of Africa (Picture), and at 530.2 carats (106.04 g)[2] was the largest polished diamond in the world until the 1985 discovery of the Golden Jubilee diamond, 545.67 carats (109.13 g), also from the Premier Mine. Cullinan I is now mounted in the head of the Sceptre with the Cross. The second largest gem from the Cullinan stone, Cullinan II or the Lesser Star of Africa, at 317.4 carats (63.48 g), is the third largest polished diamond in the world and is also part of the British crown jewels, as it forms a part of the Imperial State Crown. Both gems are on display at the Tower of London, as parts of the Crown Jewels of the United Kingdom.
In 1905, transport from South Africa to England posed a bit of a problem with regard to security. Detectives from London were placed upon a steamer ship that was rumoured to carry the stone, but this was a diversionary tactic. The stone on that ship was a fake, meant to attract those who would be interested in stealing it. The actual diamond was sent to England in a plain box via parcel post. [3]
Rumours abound of a second half of the Cullinan diamond, as there are certain indications that the diamond was part of a larger crystal. It is suggested that before Frederick Wells sold the diamond to Sir Thomas Cullinan he broke off a piece which sized in at about 1,500 to 2,000 carats (300 to 400 g). If this were true, the original Cullinan diamond would have weighed approximately 5,000 carats (1 kg)| Cullinan I Great Star of Africa | |
|---|---|
| Weight | 602.8 carats (503.4 g) |
| Color | Grade D colourless |
| Cut | |
Country of origin | South Africa |
Mine of origin | Premier Mine |
| Cut by | Asscher Brothers |
Original owner | Premier Diamond Mining Co. |
Current owner | British monarchy |
Estimated value | over £200 million, $400 million |
Designs of engagement rings have varied greatly over the years. Contemporary fashions for ring materials are a gold, platinum, silver or, rarely, titanium band mounting at least one diamond. Recently, three-stone diamond engagement rings have become popular, in contrast to the more traditional solitary diamond.
Although the establishment of the diamond engagement ring as a standard in Western culture has been attributed to one of the most successful advertising campaigns in history, by the world's leading diamond producer de Beers, in the 1940s, they were already popular and diamond engagement rings were featured in many novels from the turn of the 20th century and earlier.
An engagement ring is often significantly expensive and acts as a visible demonstration of a man's commitment to his betrothed. The rationale for using a diamond is that it is the most enduring, beautiful and expensive gem. However, some people prefer different gems or semi-precious stones such as sapphires, star sapphires, emeralds, and rubies. Pearls and opals are rare, because these are soft stones.
In some European countries such as Germany, Finland, Norway, Sweden and Denmark, engagement rings are usually plain gold bands without a gem. In others such as France, engagement rings usually mount a colored gem rather than a diamond.
Gold and platinum are recommended by many jewelers, because of their inherently higher value and because these metals are more durable than silver. Often a gold or silver ring will employ a platinum setting as it provides better protection for the stone.
Titanium and stainless steel are becoming more popular because of their lower cost and higher strength. These materials as well as traditional jewellery metals like gold and platinum that have been treated and work-hardened allow for a type of setting called a tension ring which is popular because it causes the illusion of a floating stone. Titanium and steel must be machined on a lathe because the temperatures required for proper fabrication are much too high for a small jewellery operation. A titanium ring might cause problems with removal in case of an emergency, as hospital tools are unable to cut some grades of titanium, although the titanium ring maker's FAQ challenges this notion. The results of their tests have shown that a manual ring cutter can cut through a ring in under two minutes and electric tools would be faster. Regular electrician pliers will cut a gold ring in under a second.
The inception of the engagement ring itself can be tied to the Fourth Lateran Council presided over by Pope Innocent III in 1215 . Innocent declared a longer waiting period between betrothal and marriage; plain rings of gold, silver or iron were used earliest. Gems were important and reassuring status symbols to the aristocracy. Laws were passed to preserve a visible division of social rank, ensuring only the privileged wore florid jewels. As time passed and laws relaxed, diamonds and other gems became available to the middle class.
At one time, engagement rings mounted sets of stones. One traditional sentimental pattern mounted six to celebrate the joining of two families: The birthstones of the bride's parents and the bride (on the left), and the birth stones of the groom and his parents (on the right). The parents' stones were mounted with the mother to the left of the father. The bride and groom's birthstones would be adjacent in the center. Another similar pattern, for four stones, mounted the birthstone of the parents' marriages, and the birthstones of the bride and groom. These token rings often disassembled, to expose a channel in which a lock of the suitor's hair could be treasured.
A Victorian tradition was the Regards ring, in which the initials of the precious gems used spelled out the word "regards". Another Victorian tradition was the Dearest Ring, which spelled the word "dearest" using the first letter of each jewel.
The origin of our 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 its supernatural powers. Pliny wrote that a diamond baffles poison, keeps off insanity and dispels vain fears. 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. Note: not on account of its beauty therefore, which was described by Isidore of Seville as a small stone devoid of beauty.
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.
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. Other early examples of betrothal jewels incorporating diamonds include the Bridal Crown of Blanche (ca. 1370–80) and the Heftlein brooch of Vienna (ca. 1430–40), a pictorial piece depicting a wedding couple.
The diamond engagement ring did not become the standard it is considered today until after an extensive marketing campaign by De Beers in the middle of the 20th century, which came to include one of the most famous advertising slogans of the 20th century: “A Diamond is Forever”.
In the early 20th century, the United States jewelery industry attempted to start a trend of male engagement rings, going so far as to create a supposed "historical precedent" dating back to medieval times. The attempt failed, although the industry applied lessons learned from this venture in its more successful bid to encourage the use of male wedding rings.Most commonly, the future groom will privately select and purchase a ring, to be presented to his desired bride at a future time.
With more and more couples living together prior to marriage, however, it is not unheard-of for a couple to select the engagement ring while purchasing a wedding band together. This completely eliminates the possibility of the woman not liking the engagement ring.
Refusing the gift
Women traditionally refuse offers of marriage by refusing to take the offered engagement ring. In some states of the United States, engagement rings are considered "conditional gifts" under the legal rules of property. This is an exception to the general rule that gifts cannot be revoked once properly given. See, for example, the case of Meyer v. Mitnick, 625 N.W.2d 136 (Michigan, 2001), whose ruling found the following reasoning persuasive: "the so-called 'modern trend' holds that because an engagement ring is an inherently conditional gift, once the engagement has been broken, the ring should be returned to the donor. Thus, the question of who broke the engagement and why, or who was 'at fault,' is irrelevant. This is the no-fault line of cases."
One case in New South Wales, Australia ended in the man suing his former fiancée because she threw the ring in the trash after telling her she could keep it despite the marriage proposal failing. The Supreme Court of New South Wales held that despite what the man said, the ring remained a conditional gift (partly because his saying that she could keep it was partly due to his desire to salvage the relationship) and she was ordered to pay him its AUD$15,250 cost.
Tradition generally holds that if the betrothal fails because the man himself breaks off the engagement, the woman is not obliged to return the ring. Legally, this condition can be subject to either a modified or a strict fault rule. Under the former, the fiancé can demand the return of the ring unless he breaks the engagement. Under the latter, the fiancé is entitled to the return unless his actions caused the breakup of the relationship, the same as the traditional approach. However, a no-fault rule is being advanced in some jurisdictions, under which the fiancé is always entitled to the return of the ring. The ring only becomes the property of the woman when marriage occurs. An unconditional gift approach is another possibility, wherein the ring is always treated as a gift, to be kept by the fiancée whether or not the relationship progresses to marriage. Recent court rulings have determined that the date in which the ring was offered can determine the condition of the gift. e.g. Valentine's Day and Christmas are nationally recognized as gift giving holidays. A ring offered in the form of a Christmas present will likely remain the personal property of the recipient in the event of a break up.
In the United Kingdom, the gift of an engagement ring is presumed to be an absolute gift to the fiancée. This presumption may be rebutted however by proving that the ring was given on condition (express or implied) that it must be returned if the marriage did not take place, for whatever reason. This was decided in the case Jacobs v Davis [1917] 2 KB 532.
Trading up
Traditionally, since the mid-20th century, engagement rings are a silver or gold ring, with a diamond. In modern times, the mount and ring have expanded to include platinum and other expensive metals, but the stone of choice has remained. However, whilst the global market has increased, supply is still highly regulated, and with society becoming more conscious of so-called blood diamonds, the prices of diamonds of good clarity and cut has continued to increase.
This has created a climate by which young people looking to propose to their partners are unable to afford the kind of ring tradition would dictate they should buy, but feel obliged to anyway. As a result, a new business model has sprung up, by which a person may buy a diamond (either mounted or just the stone) of lesser cost, and "trade up" to one of greater clarity or better cut as their finances allow in the future.
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Dubai: International Diamond Laboratories presented the fee structure for its diamond certification services earlier today. IDL offers scientifically based products with exclusive additional features at competitive prices. As a downstream oriented lab, the IDL is far more than just diamond certificiation. The lab provides a wealth of additional services such as sealing and certifications in a variety of languages, as well as complimentary digital certificates. The IDL also rewards its partners loyalty through a unique volume discount policy, explained Peter Meeus, CEO of IDL.
IDL offers three basic products: the IDL Diamond Certificate, the IDL Compact Diamond Certificate and the IDL Color Certificate.
• The IDL Diamond Certificate offers in a threefold luxurious cover detailed information on the 4C’s. It confirms the natural character of the diamond and offers a detailed plotting of the internal and external characteristics of the diamond. Typically, prices range from $50 for diamonds up to 46 points to $100 for a 1.99 carat stone.
• The IDL Compact Diamond Certificate is a twofold document offering detailed information on the 4C’s. It also confirms the natural character of the diamond. Compact Certificates are offered for diamonds starting from 15 points to 4.99 carats. Prices range from $35 for diamonds up to 46 points to $75 for a 1.99 carat stone.
• The IDL Color Certificate confirms that the diamond has a natural origin and that it has not been treated. It also provides the carat weight and exact color grade. The 2C Color certificate is offered at only $12 diamonds up to 46 points and $20 for stones just under a carat.
Both the diamond certificate and the compact diamond certificate come with a complimentary IDL Digicert, an electronic, online available version of the hard copy certificate that can be consulted anywhere, anytime by logging in using the certificate’s unique number.
IDL follows a very competitive and unique discount policy based on volume. Clients enjoy a discount of up to 25 percent when registering 100+ stones.
In addition, IDL offers downstream services such as sealing, laser inscription and language options at very competitive prices as part of an effort to support consumer confidence in diamonds.
• The IDL Sealing showcases the diamond in a tamper-proof container. It is fully transparent and clearly summarizes the 4C’s. Sealing is offered at just 10 USD at time of certification or $20 for resealing.
• Diamonds can be laser inscribed for $10 below a carat and $20 above. A choice is offered between the IDL logo accompanied by the certificate's unique number or a personal logo and/or message.
• Certificates can be re-issued in another language for just $10. Currently IDL certificates are available in English and Arabic.
Hong Kong: In an evening sale session before an audience hushed in anticipation, after eight tense minutes of bidding and competition between no fewer than seven telephone bidders, Sotheby’s broke an auction record which had stood for more than 20 years. Sotheby's set the per-carat record for a gemstone at auction when it sold a 6.04 carat internally-flawless emerald-cut Fancy Vivid Blue Diamond Ring for HK$61,927,500 ($7,981,835) -- (est. HK$35-48 million.)
Mr. Quek Chin Yeow, head of Sotheby’s Hong Kong Jewellery Department and deputy chairman of Sotheby’s Asia, said, “The results of today’s sale were the latest in a series of triumphs for Sotheby’s Hong Kong, which dominates the market at the top end for white and colored diamonds in Asia.
"The HK$10,252,897 ($1,321,590) price per carat achieved tonight for the internally flawless diamond, substantially exceeded the prior record price per carat of $926,000 for the Hancock Red and almost doubled the recent per carat price for a blue diamond achieved elsewhere at auction. An important emerald with a famous provenance also performed very well and a very fine collection of jadeite jewellery assembled by an important Asian private collector sparked strong competition.”
The ‘Irving Berlin Emerald’ – an Important Emerald and Diamond Sautoir, featuring an extremely rare deep, vivid green emerald weighing 47.60 carats brought the remarkable price of HK$20,487,500 ($2,640,634.) With certified Colombian origins, a renowned source for emeralds of vibrant color and fine clarity, the stone had been formerly owned by America’s best-loved songwriter and lyricist Irving Berlin and his wife Ellin Mackay.
Another magnificent colored stone, a Superb Ruby and Diamond Ring by James de Givenchy for Taffin (est. HK$12-14 million) fetched HK$14,551,500 ($1,875,543.) Set in an elegant and innovative micro-pave diamond-set frame by renowned jewellery designer James de Givenchy, nephew of the legendary fashion guru Hubert de Givenchy, the 7.20 carat ruby boasts the fabulous red color, the rarest and most sought-after of its kind.
Brilliant is the most popular cut shape for diamonds. The shape resembles that of a cone and is meant to maximize light return through the top of the diamond.
Even with modern techniques, the cutting and polishing of a diamond crystal always results in a dramatic loss of weight; rarely is it less than 50%. The round brilliant cut is preferred when the crystal is an octahedron, as often two stones may be cut from one such crystal. Oddly shaped crystals such as macles are more likely to be cut in a fancy cut—that is, a cut other than the round brilliant—which the particular crystal shape lends itself to.
The brilliant cut was introduced in the middle of the 17th century. The first brilliants were known as Mazarins. They had seventeen facets on the crown (upper half) and are called double-cut brilliants.
Vincent Peruzzi, a Venetian polisher, increased the number of crown facets from 17 to 33 (triple-cut brilliants), thereby dramatically increasing the fire and brilliance of the cut gem — already much better in the double-cut brilliant than in the rose cut. When seen today, diamonds of that cut seem quite dull compared to modern-cut ones.
Around 1900, the development of diamond saws and good jewellery lathes enabled the development of modern diamond cuts, chief among them the round brilliant cut. In 1919, Marcel Tolkowsky analyzed this cut. His calculations took both brilliance (the amount of white light reflected) and fire (flashes of spectral colors) into consideration, creating a delicate balance between the two. His geometric calculations can be found in his book on Diamond Design.
The modern round brilliant consists of 58 facets (or 57 if the culet is excluded); 33 on the crown (the top half above the middle or girdle of the stone) and 25 on the pavilion (the lower half below the girdle). In recent decades, most girdles are faceted. Many girdles have 32, 64, 80, or 96 facets; these facets are not counted in the total. While the facet count is standard, the actual proportions (crown height and angle, pavilion depth, etc.) are not universally agreed upon. One may speak of the American cut or the Scandinavian standard (Scan. D.N.), to give but two examples.
These days many people have over used Tolkowsky's "ideal" model. The original model were general guidelines as there were several aspects of diamond cut that was not explored or accounted for in the original model. Excerpts from GIA article What did Marcel Tolkowsky really say?:
Because every facet has the potential to change a light ray's plane of travel, every facet must be considered in any complete calculation of light paths. Just as a two-dimensional slice of a diamond provides incomplete information about the three-dimensional nature of light behavior inside a diamond, this two-dimensional slice also provides incomplete information about light behavior outside the diamond. A diamond's panorama is three-dimensional. Although diamonds are highly symmetrical, light can enter a diamond from many directions and many angles. This factor further highlights the need to reevaluate Tolkowsky's results, and to recalculate the effects of a diamond's proportions on its appearance aspects.
Another important point to consider is that Tolkowsky did not follow the path of a ray that was reflected more than twice in the diamond. However, we now know that a diamond's appearance is composed of many light paths that reflect considerably more than two times within that diamond. Once again, we can see that Tolkowsky's predictions are helpful in explaining optimal diamond performance, but they are incomplete by today's technological standards.
Figures 1 and 2 show the facets of a round brilliant diamond.
Figure 1 assumes that the "thick part of the girdle" is the same thickness at all 16 "thick parts". It does not consider the effects of indexed upper girdle facets.
Figure 2 is adapted from Figure 37 of Marcel Tolkowsky's Diamond Design, which was originally published in 1919. Since 1919, the lower girdle facets have become longer. As a result, the pavilion main facets have become narrower.
The relationship between the crown angle and the pavilion angle has the greatest effect on the look of the diamond. A slightly steep pavilion angle can be complemented by a shallower crown angle, and vice versa. Graphs showing this trade-off are available from folds.net.
Other proportions also affect the look of the diamond:
Several groups have developed diamond cut grading standards. They all disagree somewhat on which proportions make the best cut. There are certain proportions that are considered best by two or more groups however.
The distance from the viewer's eye to the diamond is important. The 2005 AGS cut standards are based on a distance of 25 centimeters (about 10 inches). The 2004 HCA cut standards are based on a distance of 40 centimeters (about 16 inches).
Polish and symmetry are two important aspects of the cut. The polish grade describes the smoothness of the diamond's facets, and the symmetry grade refers to alignment of the facets. With poor polish, the surface of a facet can be dulled, and may create blurred or dulled sparkle. It may constantly look like it needs to be cleaned. With poor symmetry, light can be misdirected as it enters and exits the diamond.
A number of large or extraordinarily colored 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. A partial list of famous diamonds in history follows.
Diamonds are specifically renowned as a material with superlative physical qualities — they make excellent abrasives because they can be scratched only by other diamonds, Borazon, ultrahard fullerite, or aggregated diamond nanorods, which also means they hold a polish extremely well and retain their lustre. Approximately 130 million carats (26,000 kg) are mined annually, with a total value of nearly USD $9 billion, and about 100,000 kg are synthesized annually.
The name diamond derives from the ancient Greek adamas (αδάμας; “invincible”). They have been treasured as gemstones since their use as religious icons in ancient India and usage in engraving tools also dates to early human history. Popularity of diamonds has risen since the 19th century because of increased supply, improved cutting and polishing techniques, growth in the world economy, and innovative and successful advertising campaigns. They are commonly judged by the “four Cs”: carat, clarity, color, and cut.
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 brought to the surface the diamond crystals from deep in the Earth where the high pressure and temperature enables the formation of the crystals. The mining and distribution of natural diamonds are subjects of frequent controversy such as with concerns over the sale of conflict diamonds (aka blood diamonds) by African paramilitary groups.
A diamond is a transparent crystal of tetrahedrally bonded carbon atoms and crystallizes into the face centered cubic diamond lattice structure. Diamonds have been adapted for many uses because of the material's exceptional physical characteristics. Most notable are its extreme hardness, its high dispersion index, and extremely high thermal conductivity (900 – 2320 W/m K), with a melting point of 3820 K (3547 °C / 6420 °F) and a boiling point of 5100 K (4827 °C / 8720 °F).Naturally occurring diamond has a density ranging from 3.15 to 3.53 g/cm³, with very pure diamond typically extremely close to 3.52 g/cm³.
Diamond is the hardest natural material known to man: Its hardness set to 10 (hardest) on Mohs scale of mineral hardness and having an absolute hardness value of between 90, 167, and 231 gigapascals in various tests. Diamond's hardness has been known since antiquity, and is the source of its name.
The hardest diamonds in the world are from the New England area in New South Wales, Australia. These diamonds are generally small, perfect to semiperfect octahedra, and are used to polish other diamonds. Their hardness is considered to be a product of the crystal growth form, which is single stage growth crystal. Most other diamonds show more evidence of multiple growth stages, which produce inclusions, flaws, and defect planes in the crystal lattice, all of which affect their hardness.
The hardness of diamonds contributes to its suitability as a gemstone. Because it can only be scratched by other diamonds, it maintains its polish extremely well, keeping its luster over long whiles. Unlike many other gems, it is well-suited to daily wear because of its resistance to scratching—perhaps contributing to its popularity as the preferred gem in an engagement ring or wedding ring, which are often worn every day.
Industrial use of diamonds has historically been associated with their hardness; this property 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. However, diamond is a poor choice for machining ferrous alloys at high speeds. At the high temperatures created by high speed machining, carbon is soluble in iron, leading to greatly increased wear on diamond tools as compared to other alternatives. Common industrial adaptations of this ability include diamond-tipped drill bits and saws, or use of diamond powder as an abrasive. Industrial-grade diamonds are either unsuitable for use as gems or synthetically produced, which lowers their value and makes their use economically feasible.
Other specialized applications also exist or are being developed, including use as semiconductors: some blue diamonds are natural semiconductors, in contrast to most other diamonds, which are excellent electrical insulators.
Toughness relates to a material's ability to resist breakage from forceful impact. The toughness of natural diamond has been measured as 3.4 MN m-3/2, which is good compared to other gemstones, but poor compared to most engineering materials. As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage. Diamond is therefore more fragile in some orientations than others.
Diamonds can occur in nearly any color, though yellow and brown are by far the most common. "Black" diamonds are not truly black, but rather contain numerous dark inclusions that give the gems their dark appearance. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless. Most diamond impurities 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.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).
A blue diamond recently fetched nearly $8 million. The blue hue was a result of trace amounts of boron in the stone's crystal structure.
Diamonds can be identified via their high thermal conductivity. Their high refractive index is also indicative, but other materials have similar refractivity. Diamonds do cut glass, but other materials above glass on Mohs scale such as quartz do also. Diamonds easily scratch other diamonds, but this damages both diamonds.
The formation of natural diamond requires very specific conditions. Diamond formation requires exposure of carbon-bearing materials to high pressure, ranging approximately between 45 and 60 kilobars, but at a comparatively low temperature range between approximately 1652–2372 °F (900–1300 °C). These conditions are known to be met in two places on Earth; in the lithospheric mantle below relatively stable continental plates, and at the site of a meteorite strike.
The conditions for diamond formation to happen in the lithospheric mantle occur at considerable depth corresponding to the aforementioned requirements of temperature and pressure. These depths are estimated to be in between 140–190 kilometers (90–120 miles) though occasionally diamonds have crystallized at depths of 300-400 km (180-250 miles) as well. The rate at which temperature changes with increasing depth into the Earth varies greatly in different parts of the Earth. In particular, under oceanic plates the temperature rises more quickly with depth, beyond the range required for diamond formation at the depth required. The correct combination of temperature and pressure is only found in the thick, ancient, and stable parts of continental plates where regions of lithosphere known as cratons exist.Long residence in the cratonic lithosphere allows diamond crystals to grow larger.
Through studies of carbon isotope ratios (similar to the methodology used in carbon dating, except with the stable isotopes C-12 and C-13), it has been shown that the carbon found in diamonds comes from both inorganic and organic sources. Some diamonds, known as harzburgitic, are formed from inorganic carbon originally found deep in the Earth's mantle. In contrast, eclogitic diamonds contain organic carbon 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 carbons have measurably different 13C:12C ratios. Diamonds that have come to the Earth's surface are generally very old, ranging from under 1 billion to 3.3 billion years old.
Diamonds occur most often as euhedral or rounded octahedra and twinned octahedra known as macles or maccles. As diamond'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 have rounded off and unexpressive edges and can be elongated. Sometimes they are found grown together or form double "twinned" crystals grown together at the surfaces of the octahedron. These different shapes and habits of the diamonds result from differing external circumstances. Diamonds (especially those with rounded crystal faces) are commonly found coated in nyf, an opaque gum-like skin.
Diamonds can also form in other natural high-pressure, relatively low-temperature events. Very small diamonds, known as microdiamonds or nanodiamonds, have been found in impact craters where meteors strike the Earth and create shock zones of high pressure and temperature where diamond formation can occur. Microdiamonds are now used as one indicator of ancient meteorite impact sites.
Diamond-bearing rock is brought close to the surface through deep-origin volcanic eruptions. The magma for such a volcano must originate at a depth where diamonds can be formed, 150 km (90 miles) deep or more (three times or more the depth of source magma for most volcanoes); this is a relatively rare occurrence. These typically small surface volcanic craters extend downward in formations known as volcanic pipes. The pipes contain material that was transported toward the surface by volcanic action, but was not ejected before the volcanic activity ceased. During eruption these pipes are open to the surface, resulting in open circulation; many xenoliths of surface rock and even wood and/or fossils are found in volcanic pipes. Diamond-bearing volcanic pipes are closely related to the oldest, coolest regions of continental crust (cratons). This is because cratons are very thick, and their lithospheric mantle extends to great enough depth that diamonds are stable. Not all pipes contain diamonds, and even fewer contain enough diamonds to make mining economically viable.
The magma in volcanic pipes is usually one of two characteristic types, which cool into igneous rock known as either kimberlite or lamproite. The magma itself does not contain diamond; instead, it acts as an elevator that carries deep-formed rocks (xenoliths), minerals (xenocrysts), and fluids upward. These rocks are characteristically rich in magnesium-bearing olivine, pyroxene, and amphibole minerals which are often altered to serpentine by heat and fluids during and after eruption. Certain indicator minerals typically occur within diamondiferous kimberlites and are used as mineralogic tracers by prospectors, who follow the indicator trail back to the volcanic pipe which may contain diamonds. These minerals are rich in chromium (Cr) or titanium (Ti), elements which impart bright colors to the minerals. The most common indicator minerals are chromian garnets (usually bright red Cr-pyrope, and occasionally green ugrandite-series garnets), eclogitic garnets, orange Ti-pyrope, red high-Cr spinels, dark chromite, bright green Cr-diopside, glassy green olivine, black picroilmenite, and magnetite. Kimberlite deposits are known as blue ground for the deeper serpentinized part of the deposits, or as yellow ground for the near surface smectite clay and carbonate weathered and oxidized portion.
Once diamonds have been transported to the surface by magma in a volcanic pipe, they may erode out and be distributed over a large area. A volcanic pipe containing diamonds is known as a primary source of diamonds. Secondary sources of diamonds include all areas where a significant number of diamonds, eroded out of their kimberlite or lamproite matrix, accumulate because of water or wind action. These include alluvial deposits and deposits along existing and ancient shorelines, where loose diamonds tend to accumulate because of their approximate size and density. Diamonds have also rarely been found in deposits left behind by glaciers (notably in Wisconsin and Indiana); however, in contrast to alluvial deposits, glacial deposits are not known to be of significant concentration and are therefore not viable commercial sources of diamond.
The diamond industry can be broadly separated into two basically distinct categories: one dealing with gem-grade diamonds and another for industrial-grade diamonds. While a large trade in both types of diamonds exists, the two markets act in dramatically different ways.
A large trade in gem-grade diamonds exists. Unlike precious metals such as gold or platinum, gem diamonds do not trade as a commodity: there is a substantial mark-up in the sale of diamonds, and there is not a very active market for resale of diamonds. One hallmark of the trade in gem-quality diamonds is its remarkable concentration: wholesale trade and diamond cutting is limited to a few locations (most importantly Antwerp, London, New York, Tel Aviv, Amsterdam and Surat), and a single company—De Beers—controls a significant proportion of the trade in diamonds. They are based in Johannesburg, South Africa and London, England.
The production and distribution of diamonds is largely consolidated in the hands of a few key players, and concentrated in traditional diamond trading centers. The most important being Antwerp, where 80% of all rough diamonds, 50% of all cut diamonds and more than 50% of all rough, cut and industrial diamonds combined are handled. This makes Antwerp the de facto 'world diamond capital'. New York, however, along with the rest of the United States, is where almost 80% of the world's diamonds are sold, including at auction. Also, the largest and most unusually shaped rough diamonds end up in New York. The De Beers company, as the world's largest diamond miner holds a clearly dominant position in the industry, and has done so since soon after its founding in 1888 by the British imperialist Cecil Rhodes. De Beers owns or controls a significant portion of the world's rough diamond production facilities (mines) and distribution channels for gem-quality diamonds. The company and its subsidiaries own mines that produce some 40 percent of annual world diamond production. At one time it was thought over 80 percent of the world's rough diamonds passed through the Diamond Trading Company (DTC, a subsidiary of De Beers) in London, but presently the figure is estimated at less than 50 percent.
The De Beers diamond advertising campaign is acknowledged as one of the most successful and innovative campaigns in history. N.W. Ayer & Son, the advertising firm retained by De Beers in the mid-20th century, succeeded in reviving the American diamond market and opened up new markets, even in countries where no diamond tradition had existed before. N.W. Ayer's multifaceted marketing campaign included product placement, advertising the diamond itself rather than the De Beers brand, and building associations with celebrities and royalty. This coordinated campaign has lasted decades and continues today; it is perhaps best captured by the slogan "a diamond is forever".
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. The WFDB consists of independent diamond bourses in major cutting centres such as Tel Aviv, Antwerp, Johannesburg and other cities across the USA, Europe and Asia.
In 2000, the WFDB and The International Diamond Manufacturers Association established the World Diamond Council to prevent the trading of diamonds used to fund war and inhumane acts.
WFDB's additional activities also include sponsoring the World Diamond Congress every two years, as well as the establishment of the International Diamond Council (IDC) to oversee diamond grading.
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 diamond, including clarity and color, mostly irrelevant. This helps explain why 80% of mined diamonds (equal to about 100 million carats or 20,000 kg annually), unsuitable for use as gemstones and known as bort, are destined for industrial use. In addition to mined diamonds, synthetic diamonds found industrial applications almost immediately after their invention in the 1950s; another 3 billion carats (600 metric tons) of synthetic diamond is produced annually for industrial use.
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), high-performance bearings, and limited use in specialized windows.
With the continuing advances being made in the production of synthetic diamonds, future applications are beginning to become 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 in electronics.
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.
Only a very small fraction of the diamond ore consists of actual diamonds. The ore is crushed, during which care has to be taken in order to prevent larger diamonds from being destroyed in this process and subsequently the particles are 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 known to be found only in alluvial deposits in southern India.[14] India led the world in diamond production from the time of their discovery in approximately the 9th century BCE to the mid-18th century AD, but the commercial potential of these sources had been exhausted by the late 18th century and at that time India was eclipsed by Brazil where the first non-Indian diamonds was found in 1725.
Diamond production of primary deposits (kimberlites and lamproites) only started in the 1870's after the discovery of the Diamond fields in South Africa. Production has increased over time and now an accumulated total of 4.5 billion carats have been mined since that date. Interestingly 20% of that amount has been mined in the last 5 years alone and during the last ten years, 9 new mines have started production while 4 more are awaiting opening soon. Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia.
While no commercial diamond production exists in the US, Arkansas and Colorado are the only states to have a verifiable source of diamonds.
Today, most commercially viable diamond deposits are in Russia, Botswana, Australia and the Democratic Republic of Congo. In 2005, Russia produced almost one-fifth of the global diamond output, reports the British Geological Survey. Australia boasts the richest diamondiferous pipe with production reaching peak levels of 42 Mct per year in the 1990's
There are also commercial deposits being actively mined in the Northwest Territories of Canada, Siberia (mostly in Yakutia territory, for example Mir pipe and Udachnaya pipe), Brazil, and in Northern and Western Australia. Diamond prospectors continue to search the globe for diamond-bearing kimberlite and lamproite pipes.
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 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). 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 which are not in a technical state of war and whose diamonds are therefore considered "clean."
The Canadian Government has setup a body known as Canadian Diamond Code of Conduct: 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 Diamond Trading Company, or DTC, is a subsidiary of De Beers and markets rough diamonds produced both by De Beers mines and other mines from which it purchases rough diamond production. Once purchased by sightholders, 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, and Thailand. 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 than was previously economically feasible.
Diamonds which have been prepared as gemstones are sold on diamond exchanges called bourses. There are 26 registered diamond bourses.This is 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 as is increasingly popular, 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 retail sales of US$57 billion.
Natural diamonds have formed naturally within the earth. Synthetic diamonds are created by a man-made process. A diamond simulant is defined as a non-diamond material that is used to simulate the appearance of a diamond. Diamond-simulant gems are often referred to as diamante.
The gemological and industrial uses of diamond have created a large demand for rough stones. The demand for industrial diamonds has long 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 in color and produced by so called High Pressure High Temperature (HPHT) processes. The yellow color is caused by Nitrogen impurities. 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 synthetisation.
At present the annual production of gem quality synthetic diamonds is only a few thousand carats, whereas the total production of natural diamonds is around 120 million carats. Although the production of colorless synthetic diamonds is dwarfed by that of natural diamonds, one can only find one fancy colored diamond for every 10.000 colorless ones. Since almost the complete production of synthetic diamonds consists of fancy diamonds, there is a high probability that the larger fancy colored diamonds (over 1.5 carats) will be synthetic.
Currently, trained gemologists can also distinguish between natural diamonds from synthetic diamonds. Although it has been claimed that synthetic diamonds are so perfect that it is virtually impossible to distinguish them from natural diamonds, this is not the case. Depending on the type of diamonds (either HPHT produced or CVD produced) and the color of the diamond (colored, D-Z color range or D-J color range) several methods of identification are at the disposal of a gemologist or gemlab: CVD diamonds can be identified through their orange fluorescence, D-J colored diamonds can be screened through the Swiss Gemological Organization's (SSEF) Diamond Spotter and stones in the D-Z color range can be identified through the DiamondSure UV/visible spectrometer which is a tool developed by De Beers.
A diamond's gem quality, which is not as dependent on material properties as industrial applications, has invited both imitation and the invention of procedures to enhance the gemological properties of natural diamonds. Materials which have similar gemological characteristics to diamond but are not mined or synthetic diamond are known as diamond simulants. The most familiar diamond simulant to most consumers is cubic zirconia (commonly abbreviated as CZ); recently moissanite has also gained popularity and has often been mischaracterized as a diamond simulant, although it is sold and retailed as a replacement for diamond. Both CZ and moissanite are synthetically produced. However, CZ is a diamond simulant. Diamond enhancements are specific treatments, performed on natural 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.
Currently, trained gemologists with appropriate equipment are able to distinguish natural diamonds from simulant diamonds, and they can identify all enhanced natural diamonds. Coatings are more and more used to give a diamond simulant such as Cubic Zirconia a more "Diamond like" appearance. One such substance, which is heavily advertised, is what scientists refer to as "diamond-like carbon". This is an amorphous carbonaceous material that has some physical properties which are similar to that of the diamond. Advertising suggests (righfully so or not) that such a coating would transfer some of these diamond-like properties to the coated stone, hence enhancing the diamond simulant. However, modern techniques such as Raman Spectroscopy should easily identify such as treatment.
Producing large synthetic diamonds threatens the business model of the diamond industry, and the ultimate effect of the ready availability of gem-quality diamonds at low cost in the future is hard to predict at this time.
