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The Diamonds waren eine kanadische Gesangsgruppe der er-Jahre. Ihr Gesangsstil war der Doo Wop, obwohl es sich um weiße Sänger handelte. The Diamonds waren eine kanadische Gesangsgruppe der er-Jahre. Ihr Gesangsstil war der Doo Wop, obwohl es sich um weiße Sänger handelte. Diamonds ist ein Lied von Sia Furler, Benjamin Levin, Mikkel S. Eriksen, Tor Erik Hermansen aus dem Jahr Es wurde für die aus Barbados stammende. Boron is responsible for the blue color. The associated technique is well developed; it is considered as a routine and can be performed by technicians. And Shelly Winters is N—Y usually appear light yellow or brown. Retrieved 26 September Williams, Diamond Mines of South Africa, New York, BF Buck Company, argues that the stone named " adamas " by the Greek and further referred to by Pliny was most likely a sapphire since this hoffenheim champions league qualifikation a much more abundant stone, even amongst traders in Asia, than casino verwaltung especially when used in the context of " diamonds " casino club konto loschen an ornamental stone and not used in an "industrial" context of zodiac casino paypal einzahlung gems. Cleanliness significantly affects a diamond's beauty. A diamond from the Ancient Greek: Cubic zirconia is the most common. Diamond cutters use this attribute to cleave some stones, prior to Beste Spielothek in Ehrenburg finden. Fire refers to the spectral colors which are produced as a result of the diamond dispersing the white light. Hoewever, the stronger bonds make Beste Spielothek in Hirschbronn finden less flammable. It is formed of unit cells see the figure stacked together.

Using probes such as polarized light, photoluminescence and cathodoluminescence , a series of growth zones can be identified in diamonds.

The characteristic pattern in diamonds from the lithosphere involves a nearly concentric series of zones with very thin oscillations in luminescence and alternating episodes where the carbon is resorbed by the fluid and then grown again.

Diamonds from below the lithosphere have a more irregular, almost polycrystalline texture, reflecting the higher temperatures and pressures as well as the transport of the diamonds by convection.

Geological evidence supports a model in which kimberlite magma rose at 4—20 meters per second, creating an upward path by hydraulic fracturing of the rock.

As the pressure decreases, a vapor phase exsolves from the magma, and this helps to keep the magma fluid.

At the surface, the initial eruption explodes out through fissures at high speeds over meters per second.

Then, at lower pressures, the rock is eroded, forming a pipe and producing fragmented rock breccia. As the eruption wanes, there is pyroclastic phase and then metamorphism and hydration produces serpentinites.

Although diamonds on Earth are rare, they are very common in space. In meteorites , about 3 percent of the carbon is in the form of nanodiamonds , having diameters of a few nanometers.

Sufficiently small diamonds can form in the cold of space because their lower surface energy makes them more stable than graphite.

The isotopic signatures of some nanodiamonds indicate they were formed outside the Solar System in stars. High pressure experiments predict that large quantities of diamonds condense from methane into a "diamond rain" on the ice giant planets Uranus and Neptune.

Diamonds may exist in carbon-rich stars, particularly white dwarfs. One theory for the origin of carbonado , the toughest form of diamond, is that it originated in a white dwarf or supernova.

The most familiar uses of diamonds today are as gemstones used for adornment , and as industrial abrasives for cutting hard materials.

The markets for gem-grade and industrial-grade diamonds value diamonds differently. The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds.

In the 20th century, experts in gemology developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem.

Four characteristics, known informally as the four Cs , are now commonly used as the basic descriptors of diamonds: A large, flawless diamond is known as a paragon.

A large trade in gem-grade diamonds exists. Although most gem-grade diamonds are sold newly polished, there is a well-established market for resale of polished diamonds e.

One hallmark of the trade in gem-quality diamonds is its remarkable concentration: One contributory factor is the geological nature of diamond deposits: Secondary alluvial diamond deposits, on the other hand, tend to be fragmented amongst many different operators because they can be dispersed over many hundreds of square kilometers e.

The De Beers company, as the world's largest diamond mining company, holds a dominant position in the industry, and has done so since soon after its founding in by the British imperialist Cecil Rhodes.

De Beers is currently the world's largest operator of diamond production facilities mines and distribution channels for gem-quality diamonds.

As a part of reducing its influence, De Beers withdrew from purchasing diamonds on the open market in and ceased, at the end of , purchasing Russian diamonds mined by the largest Russian diamond company Alrosa.

Botswana, Namibia, South Africa and Canada. Further down the supply chain, members of The World Federation of Diamond Bourses WFDB act as a medium for wholesale diamond exchange, trading both polished and rough diamonds.

Once purchased by Sightholders which is a trademark term referring to the companies that have a three-year supply contract with DTC , diamonds are cut and polished in preparation for sale as gemstones 'industrial' stones are regarded as a by-product of the gemstone market; they are used for abrasives.

Recently, diamond cutting centers have been established in China, India, Thailand , Namibia and Botswana. The recent expansion of this industry in India, employing low cost labor, has allowed smaller diamonds to be prepared as gems in greater quantities than was previously economically feasible.

Diamonds prepared as gemstones are sold on diamond exchanges called bourses. There are 28 registered diamond bourses in the world.

Diamonds can be sold already set in jewelry, or sold unset "loose". Mined rough diamonds are converted into gems through a multi-step process called "cutting".

Diamonds are extremely hard, but also brittle and can be split up by a single blow. Therefore, diamond cutting is traditionally considered as a delicate procedure requiring skills, scientific knowledge, tools and experience.

Its final goal is to produce a faceted jewel where the specific angles between the facets would optimize the diamond luster, that is dispersion of white light, whereas the number and area of facets would determine the weight of the final product.

For example, the diamond might be intended for display or for wear, in a ring or a necklace, singled or surrounded by other gems of certain color and shape.

Some of them are special, produced by certain companies, for example, Phoenix , Cushion , Sole Mio diamonds, etc.

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

The following issues are considered:. After initial cutting, the diamond is shaped in numerous stages of polishing. Unlike cutting, which is a responsible but quick operation, polishing removes material by gradual erosion and is extremely time consuming.

The associated technique is well developed; it is considered as a routine and can be performed by technicians. Those flaws are concealed through various diamond enhancement techniques, such as repolishing, crack filling, or clever arrangement of the stone in the jewelry.

Remaining non-diamond inclusions are removed through laser drilling and filling of the voids produced. And the firm created new markets in countries where no diamond tradition had existed before.

Ayer's marketing included product placement , advertising focused on the diamond product itself rather than the De Beers brand, and associations with celebrities and royalty.

Without advertising the De Beers brand, De Beers was advertising its competitors' diamond products as well, [91] but this was not a concern as De Beers dominated the diamond market throughout the 20th century.

De Beers still advertises diamonds, but the advertising now mostly promotes its own brands, or licensed product lines, rather than completely "generic" diamond products.

Brown-colored diamonds constituted a significant part of the diamond production, and were predominantly used for industrial purposes.

They were seen as worthless for jewelry not even being assessed on the diamond color scale. After the development of Argyle diamond mine in Australia in , and marketing, brown diamonds have become acceptable gems.

Industrial diamonds are valued mostly for their hardness and thermal conductivity, making many of the gemological characteristics of diamonds, such as the 4 Cs , irrelevant for most applications.

The boundary between gem-quality diamonds and industrial diamonds is poorly defined and partly depends on market conditions for example, if demand for polished diamonds is high, some lower-grade stones will be polished into low-quality or small gemstones rather than being sold for industrial use.

Within the category of industrial diamonds, there is a sub-category comprising the lowest-quality, mostly opaque stones, which are known as bort.

Industrial use of diamonds has historically been associated with their hardness, which makes diamond the ideal material for cutting and grinding tools.

As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds. Common industrial applications of this property include diamond-tipped drill bits and saws, and the use of diamond powder as an abrasive.

Less expensive industrial-grade diamonds, known as bort, with more flaws and poorer color than gems, are used for such purposes. Specialized applications include use in laboratories as containment for high-pressure experiments see diamond anvil cell , high-performance bearings , and limited use in specialized windows.

The high thermal conductivity of diamond makes it suitable as a heat sink for integrated circuits in electronics. The mining and distribution of natural diamonds are subjects of frequent controversy such as concerns over the sale of blood diamonds or conflict diamonds by African paramilitary groups.

Only a very small fraction of the diamond ore consists of actual diamonds. The ore is crushed, during which care is required not to destroy larger diamonds, and then sorted by density.

Today, diamonds are located in the diamond-rich density fraction with the help of X-ray fluorescence , after which the final sorting steps are done by hand.

Before the use of X-rays became commonplace, [86] the separation was done with grease belts; diamonds have a stronger tendency to stick to grease than the other minerals in the ore.

Historically, diamonds were found only in alluvial deposits in Guntur and Krishna district of the Krishna River delta in Southern India.

Diamond extraction from primary deposits kimberlites and lamproites started in the s after the discovery of the Diamond Fields in South Africa.

Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia. The Crater of Diamonds State Park in Arkansas is open to the public, and is the only mine in the world where members of the public can dig for diamonds.

Australia boasts the richest diamantiferous pipe, with production from the Argyle diamond mine reaching peak levels of 42 metric tons per year in the s.

In some of the more politically unstable central African and west African countries, revolutionary groups have taken control of diamond mines , using proceeds from diamond sales to finance their operations.

Diamonds sold through this process are known as conflict diamonds or blood diamonds. In response to public concerns that their diamond purchases were contributing to war and human rights abuses in central and western Africa, the United Nations , the diamond industry and diamond-trading nations introduced the Kimberley Process in This is done by requiring diamond-producing countries to provide proof that the money they make from selling the diamonds is not used to fund criminal or revolutionary activities.

Although the Kimberley Process has been moderately successful in limiting the number of conflict diamonds entering the market, some still find their way in.

This is a stringent tracking system of diamonds and helps protect the "conflict free" label of Canadian diamonds.

Synthetic diamonds are diamonds manufactured in a laboratory, as opposed to diamonds mined from the Earth. The gemological and industrial uses of diamond have created a large demand for rough stones.

This demand has been satisfied in large part by synthetic diamonds, which have been manufactured by various processes for more than half a century.

However, in recent years it has become possible to produce gem-quality synthetic diamonds of significant size. The majority of commercially available synthetic diamonds are yellow and are produced by so-called high-pressure high-temperature HPHT processes.

Other colors may also be reproduced such as blue, green or pink, which are a result of the addition of boron or from irradiation after synthesis.

Another popular method of growing synthetic diamond is chemical vapor deposition CVD. The growth occurs under low pressure below atmospheric pressure.

It involves feeding a mixture of gases typically 1 to 99 methane to hydrogen into a chamber and splitting them to chemically active radicals in a plasma ignited by microwaves , hot filament , arc discharge , welding torch or laser.

A diamond simulant is a non-diamond material that is used to simulate the appearance of a diamond, and may be referred to as diamante.

Cubic zirconia is the most common. The gemstone moissanite silicon carbide can be treated as a diamond simulant, though more costly to produce than cubic zirconia.

Both are produced synthetically. Diamond enhancements are specific treatments performed on natural or synthetic diamonds usually those already cut and polished into a gem , which are designed to better the gemological characteristics of the stone in one or more ways.

These include laser drilling to remove inclusions, application of sealants to fill cracks, treatments to improve a white diamond's color grade, and treatments to give fancy color to a white diamond.

Coatings are increasingly used to give a diamond simulant such as cubic zirconia a more "diamond-like" appearance. One such substance is diamond-like carbon —an amorphous carbonaceous material that has some physical properties similar to those of the diamond.

Advertising suggests that such a coating would transfer some of these diamond-like properties to the coated stone, hence enhancing the diamond simulant.

Techniques such as Raman spectroscopy should easily identify such a treatment. Early diamond identification tests included a scratch test relying on the superior hardness of diamond.

This test is destructive, as a diamond can scratch another diamond, and is rarely used nowadays. Instead, diamond identification relies on its superior thermal conductivity.

Electronic thermal probes are widely used in the gemological centers to separate diamonds from their imitations. These probes consist of a pair of battery-powered thermistors mounted in a fine copper tip.

One thermistor functions as a heating device while the other measures the temperature of the copper tip: This test takes about 2—3 seconds. Whereas the thermal probe can separate diamonds from most of their simulants, distinguishing between various types of diamond, for example synthetic or natural, irradiated or non-irradiated, etc.

Those techniques are also used for some diamonds simulants, such as silicon carbide, which pass the thermal conductivity test.

Optical techniques can distinguish between natural diamonds and synthetic diamonds. They can also identify the vast majority of treated natural diamonds.

Laboratories use techniques such as spectroscopy, microscopy and luminescence under shortwave ultraviolet light to determine a diamond's origin.

Several methods for identifying synthetic diamonds can be performed, depending on the method of production and the color of the diamond.

CVD diamonds can usually be identified by an orange fluorescence. Screening devices based on diamond type detection can be used to make a distinction between diamonds that are certainly natural and diamonds that are potentially synthetic.

Those potentially synthetic diamonds require more investigation in a specialized lab. Occasionally large thefts of diamonds take place.

The gang broke through a perimeter fence and raided the cargo hold of a Swiss-bound plane. The gang have since been arrested and large amounts of cash and diamonds recovered.

The identification of stolen diamonds presents a set of difficult problems. Rough diamonds will have a distinctive shape depending on whether their source is a mine or from an alluvial environment such as a beach or river—alluvial diamonds have smoother surfaces than those that have been mined.

Determining the provenance of cut and polished stones is much more complex. The Kimberley Process was developed to monitor the trade in rough diamonds and prevent their being used to fund violence.

Before exporting, rough diamonds are certificated by the government of the country of origin. Some countries, such as Venezuela, are not party to the agreement.

The Kimberley Process does not apply to local sales of rough diamonds within a country. Diamonds may be etched by laser with marks invisible to the naked eye.

Lazare Kaplan , a US-based company, developed this method. However, whatever is marked on a diamond can readily be removed.

Diamonds have been known in India for at least 3, years but most likely 6, years. Diamonds have been treasured as gemstones since their use as religious icons in ancient India.

Their usage in engraving tools also dates to early human history. In , the French scientist Antoine Lavoisier used a lens to concentrate the rays of the sun on a diamond in an atmosphere of oxygen , and showed that the only product of the combustion was carbon dioxide , proving that diamond is composed of carbon.

From Wikipedia, the free encyclopedia. This article is about the mineral. For the gemstone, see Diamond gemstone. The slightly misshapen octahedral shape of this rough diamond crystal in matrix is typical of the mineral.

Its lustrous faces also indicate that this crystal is from a primary deposit. Material properties of diamond. Crystallographic defects in diamond.

A round brilliant cut diamond set in a ring. Diamond cutting and Diamond cut. List of diamond mines and Exploration diamond drilling.

Kimberley Process , Blood diamond , and Child labour in the diamond industry. Gemology and Jewelry portal. Retrieved July 7, Handbook of carbon, graphite, diamond, and fullerenes: The physics of diamond.

Retrieved 31 October Reports on Progress in Physics. Laser ablation in liquids: Phase boundaries and electronic properties from first-principles theory".

Proceedings of the National Academy of Sciences. Holt, Rinehart and Winston. In Radovic, Ljubisa R. Chemistry and physics of carbon.

Their sources, descriptions and identification 5th ed. A Stable Isotope Perspective". Annual Review of Earth and Planetary Sciences.

Diamond and Related Materials. Retrieved October 28, Properties, Growth and Applications of Diamond.

Institution of Engineering and Technology. Innovative superhard materials and sustainable coatings for advanced manufacturing.

Handbook of ceramic grinding and polishing. The nature of diamonds. Retrieved 1 November Philosophical Transactions of the Royal Society A.

Retrieved March 31, Retrieved May 13, Synthetic, Imitation and Treated Gemstones. Society for Mining, Metallurgy, and Exploration.

The Mantle and Core. Archived from the original PDF on October 21, Retrieved June 16, They don't form from coal! Geology and Earth Science News and Information.

Archived from the original on October 30, Retrieved June 29, The Christian Science Monitor. Retrieved August 30, A dictionary of geology and earth sciences 4th ed.

Proceedings of Exploration Decennial Mineral Exploration Conferences , Retrieved 1 March Reviews of Modern Physics.

In laboratories and computers, shocked and squeezed matter turns metallic, coughs up diamonds and reveals Earth's white-hot center".

Retrieved 16 October Retrieved 25 September Retrieved 26 September Retrieved November 3, Archived from the original on March 17, Retrieved March 9, The Republic of Sakha.

Antwerp World Diamond Center. Retrieved September 24, Archived from the original on June 16, Retrieved April 26, Archived from the original on May 12, Archived from the original on July 5, The De Beers Group.

Archived from the original on June 13, Retrieved January 4, Retrieved May 25, Archived from the original on August 20, Retrieved August 23, Rio Tinto web site.

Archived from the original on May 11, Retrieved March 5, World Federation of Diamond Bourses. Retrieved February 12, Archived from the original on January 6, Retrieved May 5, Retrieved July 14, The cushion cut resembles a pillow and has an antique feel and a distinctive, romantic appearance.

A stunningly beautiful diamond cut with long lines that give the stone an elegant and sophisticated look.

Oval cut diamonds serve to elegantly elongate fingers, creating the optical illusion of length. Radiant Cut Diamonds combine the stylish square or rectangular shape with the brilliance of the Round Cut.

Bright, shiny and extremely clear in appearance, asscher cut diamonds allow you to see right through the stone.

The ultimate symbol of love, the heart shaped diamond is among the most romantic of the diamond shapes. Tradition and brilliance are combined in pear shaped diamonds, creating a stone which makes light 'dance.

Romantic fancy pink diamonds are often adorned by celebrities, as they are known for their luxurious feel and incredibly rarity. The rarest of all fancy color diamonds, red diamonds are perfect for the passion-seeker, evoking a deep intensity and power.

Associated with royalty and wisdom and sought after by the elite, fancy blue diamonds vary from a faint teal-blue color to a deep blue color.

Symbolizing new beginnings and growth, fancy green diamonds are adored by nature-lovers, closely connecting the wearer to nature.

A happy stone which brings a carefree sense to its wearer, fancy color orange diamonds range in shades from light orange to fancy deep orange.

Fancy brown diamonds are becoming increasingly popular, the champagne hues providing an elegant and classy feel to whoever adorns the stone.

Fancy grey diamonds come in varying shades, from pewter to graphite, and are perfect for the sophisticated, modern women. Select from hundreds of stunning engagement ring styles and add a brilliant loose diamond of your choice.

Every loose diamond on JamesAllen. The diamond certificates are displayed along with the loose diamond on our site. True to their name, the patterned reflection of hearts and arrows only appears when the diamond is of this absolute symmetry.

The hearts are seen from the bottom of the diamond the pointed side and the arrows are seen from the top. Fancy color diamonds are a beautiful choice for those who want an alternative to the traditional "colorless" diamond.

Choose a brilliant fancy color diamond in yellow, pink, purple red, blue, green, orange, brown, black or gray for a unique, colorful diamond engagement ring.

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Design your engagement ring with the perfect loose diamond. Find your favorite loose diamond. Click the Real-Time Diamond Inspection button. Princess Cut The second most popular of the diamond shapes, the princess cut is designed for maximum brilliance.

Cushion Cut The cushion cut resembles a pillow and has an antique feel and a distinctive, romantic appearance.

Emerald Cut A stunningly beautiful diamond cut with long lines that give the stone an elegant and sophisticated look. Oval Oval cut diamonds serve to elegantly elongate fingers, creating the optical illusion of length.

Radiant Radiant Cut Diamonds combine the stylish square or rectangular shape with the brilliance of the Round Cut.

Asscher Bright, shiny and extremely clear in appearance, asscher cut diamonds allow you to see right through the stone.

Heart The ultimate symbol of love, the heart shaped diamond is among the most romantic of the diamond shapes. Pear Tradition and brilliance are combined in pear shaped diamonds, creating a stone which makes light 'dance.

Brown Fancy brown diamonds are becoming increasingly popular, the champagne hues providing an elegant and classy feel to whoever adorns the stone.

Fancy Color Diamonds Fancy color diamonds are a beautiful choice for those who want an alternative to the traditional "colorless" diamond.

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Plastic deformation is the cause of color in some brown [38] and perhaps pink and red diamonds. 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.

Diamonds of a different color, such as blue, are called fancy colored diamonds and fall under a different grading scale.

In , the Wittelsbach Diamond , a Diamonds can be identified by their high thermal conductivity.

Their high refractive index is also indicative, but other materials have similar refractivity. Diamonds cut glass, but this does not positively identify a diamond because other materials, such as quartz, also lie above glass on the Mohs scale and can also cut it.

Diamonds can scratch other diamonds, but this can result in damage to one or both stones. Hardness tests are infrequently used in practical gemology because of their potentially destructive nature.

Diamonds also possess an extremely high refractive index and fairly high dispersion. Taken together, these factors affect the overall appearance of a polished diamond and most diamantaires still rely upon skilled use of a loupe magnifying glass to identify diamonds "by eye".

Diamonds are extremely rare, with concentrations of at most parts per billion in source rock. Loose diamonds are also found along existing and ancient shorelines , where they tend to accumulate because of their size and density.

Most diamonds come from the Earth's mantle , and most of this section discusses those diamonds. However, there are other sources.

Some blocks of the crust, or terranes , have been buried deep enough as the crust thickened so they experienced ultra-high-pressure metamorphism.

These have evenly distributed microdiamonds that show no sign of transport by magma. In addition, when meteorites strike the ground, the shock wave can produce high enough temperatures and pressures for microdiamonds and nanodiamonds to form.

A common misconception is that diamonds are formed from highly compressed coal. Coal is formed from buried prehistoric plants, and most diamonds that have been dated are far older than the first land plants.

It is possible that diamonds can form from coal in subduction zones , but diamonds formed in this way are rare, and the carbon source is more likely carbonate rocks and organic carbon in sediments, rather than coal.

Diamonds are far from evenly distributed over the Earth. A rule of thumb known as Clifford's rule states that they are almost always found in kimberlites on the oldest part of cratons , the stable cores of continents with typical ages of 2.

The Argyle diamond mine in Australia , the largest producer of diamonds by weight in the world, is located in a mobile belt , also known as an orogenic belt , [53] a weaker zone surrounding the central craton that has undergone compressional tectonics.

Instead of kimberlite, the host rock is lamproite. Lamproites with diamonds that are not economically viable are also found in the United States, India and Australia.

Kimberlites can be found in narrow 1—4 meters dikes and sills, and in pipes with diameters that range from about 75 meters to 1.

Fresh rock is dark bluish green to greenish gray, but after exposure rapidly turns brown and crumbles. They are a mixture of xenocrysts and xenoliths minerals and rocks carried up from the lower crust and mantle , pieces of surface rock, altered minerals such as serpentine , and new minerals that crystallized during the eruption.

The texture varies with depth. The composition forms a continuum with carbonatites , but the latter have too much oxygen for carbon to exist in a pure form.

Instead, it is locked up in the mineral calcite Ca C O 3. All three of the diamond-bearing rocks kimberlite, lamproite and lamprophyre lack certain minerals melilite and kalsilite that are incompatible with diamond formation.

In kimberlite, olivine is large and conspicuous, while lamproite has Ti- phlogopite and lamprophyre has biotite and amphibole.

They are all derived from magma types that erupt rapidly from small amounts of melt, are rich in volatiles and magnesium oxide , and are less oxidizing than more common mantle melts such as basalt.

These characteristics allow the melts to carry diamonds to the surface before they dissolve. Kimberlite pipes can be difficult to find. They weather quickly within a few years after exposure and tend to have lower topographic relief than surrounding rock.

If they are visible in outcrops, the diamonds are never visible because they are so rare. In any case, kimberlites are often covered with vegetation, sediments, soils or lakes.

In modern searches, geophysical methods such as aeromagnetic surveys , electrical resistivity and gravimetry , help identify promising regions to explore.

This is aided by isotopic dating and modeling of the geological history. Then surveyors must go to the area and collect samples, looking for kimberlite fragments or indicator minerals.

The latter have compositions that reflect the conditions where diamonds form, such as extreme melt depletion or high pressures in eclogites.

However, indicator minerals can be misleading; a better approach is geothermobarometry , where the compositions of minerals are analyzed as if they were in equilibrium with mantle minerals.

Finding kimberlites requires persistence, and only a small fraction contain diamonds that are commercially viable. The only major discoveries since about have been in Canada.

Since existing mines have lifetimes of as little as 25 years, there could be a shortage of new diamonds in the future. Diamonds are dated by analyzing inclusions using the decay of radioactive isotopes.

Depending on the elemental abundances, one can look at the decay of rubidium to strontium , samarium to neodymium , uranium to lead , argon to argon , or rhenium to osmium.

Those found in kimberlites have ages ranging from 1 to 3. The kimberlites themselves are much younger. Most of them have ages between tens of millions and million years old, although there are some older exceptions Argyle, Premier and Wawa.

Thus, the kimberlites formed independently of the diamonds and served only to transport them to the surface. The reason for the lack of older kimberlites is unknown, but it suggests there was some change in mantle chemistry or tectonics.

No kimberlite has erupted in human history. Most gem-quality diamonds come from depths of to kilometers in the lithosphere.

Such depths occur below cratons in mantle keels , the thickest part of the lithosphere. These regions have high enough pressure and temperature to allow diamonds to form and they are not convecting, so diamonds can be stored for billions of years until a kimberlite eruption samples them.

Host rocks in a mantle keel include harzburgite and lherzolite , two type of peridotite. The most dominant rock type in the upper mantle, peridotite is an igneous rock consisting mostly of the minerals olivine and pyroxene ; it is low in silica and high in magnesium.

However, diamonds in peridotite rarely survive the trip to the surface. A smaller fraction of diamonds about have been studied come from depths of — kilometers, a region that includes the transition zone.

They formed in eclogite but are distinguished from diamonds of shallower origin by inclusions of majorite a form of garnet with excess silicon.

A similar proportion of diamonds comes from the lower mantle at depths between and kilometers. Diamond is thermodynamically stable at high pressures and temperatures, with the phase transition from graphite occurring at greater temperatures as the pressure increases.

Thus, underneath continents it becomes stable at temperatures of degrees Celsius and pressures of 4. In subduction zones, which are colder, it becomes stable at temperatures of degrees C and pressures of 3.

At depths greater than km, iron-nickel metal phases are present and carbon is likely to be either dissolved in them or in the form of carbides.

Thus, the deeper origin of some diamonds may reflect unusual growth environments. In the first known natural samples of a phase of ice called Ice VII were found as inclusions in diamond samples.

The inclusions formed at depths between and kilometers, straddling the upper and lower mantle, and provide evidence for water-rich fluid at these depths.

The amount of carbon in the mantle is not well constrained, but its concentration is estimated at 0. This ratio has a wide range in meteorites, which implies that it was probably also broad in the early Earth.

It can also be altered by surface processes like photosynthesis. Common rocks from the mantle such as basalts, carbonatites and kimberlites have ratios between -8 and On the surface, organic sediments have an average of while carbonates have an average of 0.

This variability implies that they are not formed from carbon that is primordial having resided in the mantle since the Earth formed.

Instead, they are the result of tectonic processes, although given the ages of diamonds not necessarily the same tectonic processes that act in the present.

Diamonds in the mantle form through a metasomatic process where a C-O-H-N-S fluid or melt dissolves minerals in a rock and replaces them with new minerals.

Diamonds form from this fluid either by reduction of oxidized carbon e. Using probes such as polarized light, photoluminescence and cathodoluminescence , a series of growth zones can be identified in diamonds.

The characteristic pattern in diamonds from the lithosphere involves a nearly concentric series of zones with very thin oscillations in luminescence and alternating episodes where the carbon is resorbed by the fluid and then grown again.

Diamonds from below the lithosphere have a more irregular, almost polycrystalline texture, reflecting the higher temperatures and pressures as well as the transport of the diamonds by convection.

Geological evidence supports a model in which kimberlite magma rose at 4—20 meters per second, creating an upward path by hydraulic fracturing of the rock.

As the pressure decreases, a vapor phase exsolves from the magma, and this helps to keep the magma fluid. At the surface, the initial eruption explodes out through fissures at high speeds over meters per second.

Then, at lower pressures, the rock is eroded, forming a pipe and producing fragmented rock breccia. As the eruption wanes, there is pyroclastic phase and then metamorphism and hydration produces serpentinites.

Although diamonds on Earth are rare, they are very common in space. In meteorites , about 3 percent of the carbon is in the form of nanodiamonds , having diameters of a few nanometers.

Sufficiently small diamonds can form in the cold of space because their lower surface energy makes them more stable than graphite.

The isotopic signatures of some nanodiamonds indicate they were formed outside the Solar System in stars. High pressure experiments predict that large quantities of diamonds condense from methane into a "diamond rain" on the ice giant planets Uranus and Neptune.

Diamonds may exist in carbon-rich stars, particularly white dwarfs. One theory for the origin of carbonado , the toughest form of diamond, is that it originated in a white dwarf or supernova.

The most familiar uses of diamonds today are as gemstones used for adornment , and as industrial abrasives for cutting hard materials.

The markets for gem-grade and industrial-grade diamonds value diamonds differently. The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds.

In the 20th century, experts in gemology developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem.

Four characteristics, known informally as the four Cs , are now commonly used as the basic descriptors of diamonds: A large, flawless diamond is known as a paragon.

A large trade in gem-grade diamonds exists. Although most gem-grade diamonds are sold newly polished, there is a well-established market for resale of polished diamonds e.

One hallmark of the trade in gem-quality diamonds is its remarkable concentration: One contributory factor is the geological nature of diamond deposits: Secondary alluvial diamond deposits, on the other hand, tend to be fragmented amongst many different operators because they can be dispersed over many hundreds of square kilometers e.

The De Beers company, as the world's largest diamond mining company, holds a dominant position in the industry, and has done so since soon after its founding in by the British imperialist Cecil Rhodes.

De Beers is currently the world's largest operator of diamond production facilities mines and distribution channels for gem-quality diamonds.

As a part of reducing its influence, De Beers withdrew from purchasing diamonds on the open market in and ceased, at the end of , purchasing Russian diamonds mined by the largest Russian diamond company Alrosa.

Botswana, Namibia, South Africa and Canada. Further down the supply chain, members of The World Federation of Diamond Bourses WFDB act as a medium for wholesale diamond exchange, trading both polished and rough diamonds.

Once purchased by Sightholders which is a trademark term referring to the companies that have a three-year supply contract with DTC , diamonds are cut and polished in preparation for sale as gemstones 'industrial' stones are regarded as a by-product of the gemstone market; they are used for abrasives.

Recently, diamond cutting centers have been established in China, India, Thailand , Namibia and Botswana. The recent expansion of this industry in India, employing low cost labor, has allowed smaller diamonds to be prepared as gems in greater quantities than was previously economically feasible.

Diamonds prepared as gemstones are sold on diamond exchanges called bourses. There are 28 registered diamond bourses in the world. Diamonds can be sold already set in jewelry, or sold unset "loose".

Mined rough diamonds are converted into gems through a multi-step process called "cutting". Diamonds are extremely hard, but also brittle and can be split up by a single blow.

Therefore, diamond cutting is traditionally considered as a delicate procedure requiring skills, scientific knowledge, tools and experience.

Its final goal is to produce a faceted jewel where the specific angles between the facets would optimize the diamond luster, that is dispersion of white light, whereas the number and area of facets would determine the weight of the final product.

For example, the diamond might be intended for display or for wear, in a ring or a necklace, singled or surrounded by other gems of certain color and shape.

Some of them are special, produced by certain companies, for example, Phoenix , Cushion , Sole Mio diamonds, etc. The most time-consuming part of the cutting is the preliminary analysis of the rough stone.

It needs to address a large number of issues, bears much responsibility, and therefore can last years in case of unique diamonds.

The following issues are considered:. After initial cutting, the diamond is shaped in numerous stages of polishing.

Unlike cutting, which is a responsible but quick operation, polishing removes material by gradual erosion and is extremely time consuming.

The associated technique is well developed; it is considered as a routine and can be performed by technicians. Those flaws are concealed through various diamond enhancement techniques, such as repolishing, crack filling, or clever arrangement of the stone in the jewelry.

Remaining non-diamond inclusions are removed through laser drilling and filling of the voids produced. And the firm created new markets in countries where no diamond tradition had existed before.

Ayer's marketing included product placement , advertising focused on the diamond product itself rather than the De Beers brand, and associations with celebrities and royalty.

Without advertising the De Beers brand, De Beers was advertising its competitors' diamond products as well, [91] but this was not a concern as De Beers dominated the diamond market throughout the 20th century.

De Beers still advertises diamonds, but the advertising now mostly promotes its own brands, or licensed product lines, rather than completely "generic" diamond products.

Brown-colored diamonds constituted a significant part of the diamond production, and were predominantly used for industrial purposes.

They were seen as worthless for jewelry not even being assessed on the diamond color scale. After the development of Argyle diamond mine in Australia in , and marketing, brown diamonds have become acceptable gems.

Industrial diamonds are valued mostly for their hardness and thermal conductivity, making many of the gemological characteristics of diamonds, such as the 4 Cs , irrelevant for most applications.

The boundary between gem-quality diamonds and industrial diamonds is poorly defined and partly depends on market conditions for example, if demand for polished diamonds is high, some lower-grade stones will be polished into low-quality or small gemstones rather than being sold for industrial use.

Within the category of industrial diamonds, there is a sub-category comprising the lowest-quality, mostly opaque stones, which are known as bort.

Industrial use of diamonds has historically been associated with their hardness, which makes diamond the ideal material for cutting and grinding tools.

As the hardest known naturally occurring material, diamond can be used to polish, cut, or wear away any material, including other diamonds. Common industrial applications of this property include diamond-tipped drill bits and saws, and the use of diamond powder as an abrasive.

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

Specialized applications include use in laboratories as containment for high-pressure experiments see diamond anvil cell , high-performance bearings , and limited use in specialized windows.

The high thermal conductivity of diamond makes it suitable as a heat sink for integrated circuits in electronics. The mining and distribution of natural diamonds are subjects of frequent controversy such as concerns over the sale of blood diamonds or conflict diamonds by African paramilitary groups.

Only a very small fraction of the diamond ore consists of actual diamonds. The ore is crushed, during which care is required not to destroy larger diamonds, and then sorted by density.

Today, diamonds are located in the diamond-rich density fraction with the help of X-ray fluorescence , after which the final sorting steps are done by hand.

Before the use of X-rays became commonplace, [86] the separation was done with grease belts; diamonds have a stronger tendency to stick to grease than the other minerals in the ore.

Historically, diamonds were found only in alluvial deposits in Guntur and Krishna district of the Krishna River delta in Southern India.

Diamond extraction from primary deposits kimberlites and lamproites started in the s after the discovery of the Diamond Fields in South Africa.

Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia. The Crater of Diamonds State Park in Arkansas is open to the public, and is the only mine in the world where members of the public can dig for diamonds.

Australia boasts the richest diamantiferous pipe, with production from the Argyle diamond mine reaching peak levels of 42 metric tons per year in the s.

In some of the more politically unstable central African and west African countries, revolutionary groups have taken control of diamond mines , using proceeds from diamond sales to finance their operations.

Diamonds sold through this process are known as conflict diamonds or blood diamonds. In response to public concerns that their diamond purchases were contributing to war and human rights abuses in central and western Africa, the United Nations , the diamond industry and diamond-trading nations introduced the Kimberley Process in This is done by requiring diamond-producing countries to provide proof that the money they make from selling the diamonds is not used to fund criminal or revolutionary activities.

Although the Kimberley Process has been moderately successful in limiting the number of conflict diamonds entering the market, some still find their way in.

This is a stringent tracking system of diamonds and helps protect the "conflict free" label of Canadian diamonds. Synthetic diamonds are diamonds manufactured in a laboratory, as opposed to diamonds mined from the Earth.

The gemological and industrial uses of diamond have created a large demand for rough stones. This demand has been satisfied in large part by synthetic diamonds, which have been manufactured by various processes for more than half a century.

However, in recent years it has become possible to produce gem-quality synthetic diamonds of significant size. The majority of commercially available synthetic diamonds are yellow and are produced by so-called high-pressure high-temperature HPHT processes.

Other colors may also be reproduced such as blue, green or pink, which are a result of the addition of boron or from irradiation after synthesis. Another popular method of growing synthetic diamond is chemical vapor deposition CVD.

The growth occurs under low pressure below atmospheric pressure. It involves feeding a mixture of gases typically 1 to 99 methane to hydrogen into a chamber and splitting them to chemically active radicals in a plasma ignited by microwaves , hot filament , arc discharge , welding torch or laser.

A diamond simulant is a non-diamond material that is used to simulate the appearance of a diamond, and may be referred to as diamante.

Cubic zirconia is the most common. The gemstone moissanite silicon carbide can be treated as a diamond simulant, though more costly to produce than cubic zirconia.

Both are produced synthetically. Diamond enhancements are specific treatments performed on natural or synthetic diamonds usually those already cut and polished into a gem , which are designed to better the gemological characteristics of the stone in one or more ways.

These include laser drilling to remove inclusions, application of sealants to fill cracks, treatments to improve a white diamond's color grade, and treatments to give fancy color to a white diamond.

Coatings are increasingly used to give a diamond simulant such as cubic zirconia a more "diamond-like" appearance. One such substance is diamond-like carbon —an amorphous carbonaceous material that has some physical properties similar to those of the diamond.

Advertising suggests that such a coating would transfer some of these diamond-like properties to the coated stone, hence enhancing the diamond simulant.

Techniques such as Raman spectroscopy should easily identify such a treatment. Early diamond identification tests included a scratch test relying on the superior hardness of diamond.

This test is destructive, as a diamond can scratch another diamond, and is rarely used nowadays. Instead, diamond identification relies on its superior thermal conductivity.

Electronic thermal probes are widely used in the gemological centers to separate diamonds from their imitations.

These probes consist of a pair of battery-powered thermistors mounted in a fine copper tip. One thermistor functions as a heating device while the other measures the temperature of the copper tip: This test takes about 2—3 seconds.

Whereas the thermal probe can separate diamonds from most of their simulants, distinguishing between various types of diamond, for example synthetic or natural, irradiated or non-irradiated, etc.

Those techniques are also used for some diamonds simulants, such as silicon carbide, which pass the thermal conductivity test. Optical techniques can distinguish between natural diamonds and synthetic diamonds.

They can also identify the vast majority of treated natural diamonds. Laboratories use techniques such as spectroscopy, microscopy and luminescence under shortwave ultraviolet light to determine a diamond's origin.

Several methods for identifying synthetic diamonds can be performed, depending on the method of production and the color of the diamond. CVD diamonds can usually be identified by an orange fluorescence.

Screening devices based on diamond type detection can be used to make a distinction between diamonds that are certainly natural and diamonds that are potentially synthetic.

Those potentially synthetic diamonds require more investigation in a specialized lab. Occasionally large thefts of diamonds take place.

The gang broke through a perimeter fence and raided the cargo hold of a Swiss-bound plane. The gang have since been arrested and large amounts of cash and diamonds recovered.

The identification of stolen diamonds presents a set of difficult problems. Rough diamonds will have a distinctive shape depending on whether their source is a mine or from an alluvial environment such as a beach or river—alluvial diamonds have smoother surfaces than those that have been mined.

Determining the provenance of cut and polished stones is much more complex. The Kimberley Process was developed to monitor the trade in rough diamonds and prevent their being used to fund violence.

Before exporting, rough diamonds are certificated by the government of the country of origin. Some countries, such as Venezuela, are not party to the agreement.

The Kimberley Process does not apply to local sales of rough diamonds within a country. Diamonds may be etched by laser with marks invisible to the naked eye.

Lazare Kaplan , a US-based company, developed this method. However, whatever is marked on a diamond can readily be removed. Diamonds have been known in India for at least 3, years but most likely 6, years.

Diamonds have been treasured as gemstones since their use as religious icons in ancient India. A young British woman suffering from depression over the loss of her husband develops an unusual relationship with her chauffeur.

A group of Mexican revolutionaries murders a town priest and a number of his christian followers. Ten years later, a widow arrives in town intent to take revenge from her husband's killers.

Tish Gray had a baby and gave it up for adoption. She is contacted by a second childless couple who want her to have the husband's baby because of the wife's inability to have children.

An American returns to his native Dutch village in the nineteen thirties and causes a sensation there.

When his pregnant daughter starts an affair with the son of the local cheese-factory Black Sunday is the powerful story of a Black September terrorist group attempting to blow up a Goodyear blimp hovering over the Super Bowl stadium with 80, people and the president of the United States in attendance.

Two escapees are on the run in the wilderness of an unspecified country. Wherever they go, they are followed by a menacing black helicopter.

In Bermuda, two amateur treasure-hunting divers have a run-in with local criminals when they inadvertently discover the secret cargo of a World War II shipwreck.

Firstly, it is wrong to associate this alongside any of the Shaft series. Roundtree is entirely cast different, and fans of Shaft will be disappointed that he doesn't even wear a mustache in the film.

It's hardly jaw-dropping material, but Golan of the Cannon film group invested well into this accurately sketched story.

The location work on "Diamonds" is superb and justly highlighted. The story starts in Europe but is mostly in the streets, neighborhoods and buildings of Israel, which is somewhat unusual for an "exotic" locale.

There's plenty of local flavor injected into the story, and the location plays a big part in the tension of the plot- Israeli police using their own means to track down an international thief and an ominous London businessman.

Roundtree is superb, still shining in the Shaft afterglow and Shaw is as consistent as ever even in the iffy double-casting job. Unfortunately, the women do not fare so well- Barbara Hershey as Barbara Seagull whines at Roundtree's character throughout half the film about some unclear relationship issues.

And Shelly Winters is She plays a stereotype American Jewish woman visiting Israel on a tour to buy diamonds. Nonetheless, the action and details of this thriller are the fenceposts here and they hold together a remarkably good 70's flick.

It too has been reissued. Overall, it's a nice surprise and I recommend it to anyone who enjoys 70's action cinema or borderline Black action.

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