Diamond is a solid form of carbon with a cubic diamond crystal structure. At room temperature and pressure it is metastable and graphite is a stable form, but diamonds almost never turn into graphite. Diamond is famous for its superlative physical qualities, most of which come from strong covalent bonds between the atoms. In particular, it has the highest hardness and thermal conductivity of any bulk material. These properties determine the major industrial applications of diamond in cutting and polishing scientific tools and applications in diamond blades and diamond anvil cells.
Because of the very rigid lattice, diamonds can be contaminated by very few types of impurities, such as boron and nitrogen. A small number of defects or impurities (about one per million grating atoms) are diamond blue (boron), yellow (nitrogen), brown (lattice defects), green (radiation exposure), purple, pink, orange or red. Diamonds also have relatively high optical dispersions (the ability to dissolve light with different colors).
Most natural diamonds have an age ranging from 1 billion to 3.5 billion years. Mostly formed at a depth of 150 to 250 kilometers (93 to 155Ã, mi) in Earth's mantle, though some have come from as deep as 800 kilometers (500 mi). Under high pressure and temperature, carbon-containing liquids dissolve minerals and replace them with diamonds. Much newer (tens to hundreds of millions of years ago), they were brought to the surface in volcanic eruptions and stored in igneous rocks known as kimberlites and lamproites.
Diamonds can be produced synthetically in high-pressure, high-temperature (HPHT) methods that roughly simulate conditions in Earth's mantle. The alternative, and completely different growth techniques are chemical vapor deposition (CVD). Some non-diamond materials, which include cubic zirconia and silicon carbide and often called diamond simulants, resemble diamonds in appearance and many properties. Special gemological techniques have been developed to distinguish natural diamonds, synthetic diamonds, and diamond simulants.
Video Diamond
History
The name diamond comes from the ancient Greek ?????? (adÃÆ'¡mas ), "right", "unchangeable", "Unbreakable", "untamed", from? - (a-), "un-" ????? ( damÃÆ'¡? ), "I beat", "I'm tame". Diamonds are considered first known and mined in India, where significant alluvial deposits of stone can be found centuries ago along the Penner, Krishna and Godavari rivers. Diamonds have been known in India for at least 3,000 years but most likely 6,000 years.
Diamonds have been valuable as gems since being used as religious icons in ancient India. Their use in carving tools also comes from ancient human history. The popularity of diamonds has increased since the 19th century due to increased supply, improved cutting and polishing techniques, world economic growth, and innovative and successful advertising campaigns.
In 1772, French scientist Antoine Lavoisier used lenses to concentrate sunlight on diamonds in the oxygen atmosphere, and showed that the only product of combustion was carbon dioxide, proving that diamonds consist of carbon. Then in 1797, the British chemist Smithson Tennant repeated and expanded the experiment. By showing that diamond burning and graphite release the same amount of gas, it establishes the chemical equivalence of these substances.
The best known diamond use today is gems used for jewelry, and as industrial abrasive materials for cutting hard materials. The dispersion of white light into spectral colors is a major gemological characteristic of gem gems. In the 20th century, gemologists developed methods of giving diamonds and other gemstones based on the characteristics most important to their value as gems. Four characteristics, known informally as four Cs , are now commonly used as basic diamond descriptions: these are carat (weights), cut (quality the cut is judged by proportion, symmetry and polish), colors (how close to white or colorless, to fancy diamonds to how intense the hue is), and clarity (how free from inclusion). The immaculate large diamond is known as the paragon.
Maps Diamond
Geology
Diamonds are extremely rare, with the most concentrations per billion source rocks. Before the 20th century, most diamonds were found in alluvial deposits. Loose diamonds are also found along the existing and ancient coastline, where they tend to accumulate because of their size and density. Rarely, they have been found in glacial up (especially in Wisconsin and Indiana), but these deposits are not of commercial quality. This type of deposit comes from local frozen rock intrusions through weathering and transport by wind or water.
Most diamonds come from Earth's mantle, and most of this section discusses the diamond. However, there are other sources. Some blocks of the crust, or terran, have been buried deep enough because the crust is thickened so that they experience ultra high-pressure metamorphism. This has evenly distributed microdiamonds that show no sign of transportation by magma. In addition, when the meteorite strikes the ground, the shock wave can produce a high enough temperature and pressure for microdiamonds and nanodiamonds to form. Type-impact microdiamonds can be used as an ancient impact crater indicator. Russia's Popigai crater may have the largest diamond deposit in the world, estimated at trillions of rust, and is formed by asteroid impacts.
A common misconception is that diamonds are formed from high compressed coal. Coal is made up of prehistoric plants buried, and most diamonds are much older than the first land plants. It is possible that diamonds can be formed from coal in subduction zones, but diamonds formed in this way are rare, and carbon sources are more likely rocks of carbonates and organic carbon in sediments, than coal.
Surface distribution
Diamonds are far from evenly distributed on Earth. A general rule known as the Clifford rule states that they are almost always found in kimberlites in the oldest part of the crater, a stable continental core with a typical age of 2.5 billion years or more. However, there are exceptions. Argyle diamond mine in Australia, the world's largest manufacturer of diamonds, is located in the cellular belt , also known as the orogenic belt , the weaker zone around it. the central kraton which has undergone compressional tectonics. Instead of kimberlite, the parent rock is lamproite. Lamproites with uneconomical diamonds are also found in the United States, India and Australia. In addition, diamonds in the Wawa belt of Superior province in Canada and microdiamond in the Japanese island arc are found in a type of rock called lamprophyre.
Kimberlites can be found on narrow dikes (1-4 meters) and sills, and in pipes with diameters ranging from about 75 meters to 1.5 kilometers. Fresh green stone is bluish-green to greenish gray, but after exposure it quickly turns brown and crushed. This is a hybrid rock with a mixture of small minerals and clay fragments (clasts) are chaotic to the size of watermelon. They are a mixture of xenocrysts and xenoliths (minerals and stones brought from the crust and lower mantle), surface stone pieces, altered minerals such as serpentine, and new minerals that crystallize during eruptions. The texture varies with depth. Its composition forms a continuum with carbonate, but the latter has too much oxygen for carbon to exist in its pure form. Instead, it is enclosed in calcite minerals (CaCO 3 ).
The three diamond-containing stones (kimberlite, lamproite and lamprophyre) lack specific minerals (melilite and calcylite) that are incompatible with the diamond formation. In kimberlite, olivine is large and striking, while lamproite has Ti-phlogopite and lamprophyre has biotite and amphibole. They all come from a type of magma that erupts rapidly from small amounts of melting, rich in volatiles and magnesium oxide, and less oxidize than the more common melting coats like basalts. These characteristics allow melt to bring diamonds to the surface before they dissolve.
Exploration
Kimberlite pipes can be hard to find. They weather fast (within a few years after exposure) and tend to have a lower topography relief than the surrounding rocks. If they are visible in the outcrop, diamonds are never seen because they are so rare. In any case, kimberlite is often covered with vegetation, sediment, soil or lake. In modern searches, geophysical methods such as aeromagnetic surveys, electrical resistivity and gravimetry, help identify areas that promise to be explored. This is aided by an isotope dating and geological history modeling. Then the surveyor must go to the area and collect samples, look for kimberlite fragments or mineral indicators . The latter has a composition that reflects the conditions in which the shape of a diamond, such as extreme melting depletion or high pressure in eclogites. However, mineral indicators can be misleading; a better approach is geothermobarometry, where mineral compositions are analyzed as if they are in equilibrium with mineral mantle.
Finding kimberlite requires perseverance, and only a small portion contains commercially viable diamonds. The only major invention since around 1980 is in Canada. Since the existing mine has a minimum life span of 25 years, there may be a shortage of new diamonds in the future.
Century
Diamonds are dated by analyzing inclusions using radioactive isotope decay. Depending on the abundance of the elements, one can see rubidium weathering to strontium, samarium to neodymium, uranium to lead, argon-40 to argon-39, or rhenium to osmium. What is found in kimberlit has an age ranging from 1 to 3.5 billion years old, and there can be several ages in the same kimberlit, showing some episodes of diamond formation. The kimberlites themselves are much younger. Most of them have an age between tens of millions and 300 million years, although there are some older exceptions (Argyle, Premier and Wawa). Thus, the kimberlite is formed independently of the diamond and serves only to transport it to the surface. Kimberlites are also much younger than the craters they have erupted. The reason for the lack of an older kimberlite is unknown, but it shows there are some changes in mantle or tectonic chemistry. No kimberlite erupts in human history.
Origin in the mantle
Most gem-quality diamonds come from a depth of 150 to 250 kilometers in the lithosphere. Such depths occur beneath the crater in the mantle keels, the thickest part of the lithosphere. These areas have high enough pressure and temperature to allow diamonds to form and they are not convincing, so diamonds can be stored for billions of years until kimberlite eruption scales them.
The master rocks in the mantle sheath include harzburgite and lherzolite, two types of peridotite. The most dominant type of rock in the upper mantle, the peridotite is igneous rock consisting mostly of olivine and pyroxene minerals; it is low in silica and high in magnesium. However, diamonds on the peridotite rarely survive from travel to the surface. Another common source keeping intact intact is eclogite, a metamorphic rock usually formed from basalt when oceanic plates plunge into the mantle in the subduction zone.
A small diamond (about 150 have been studied) comes from a depth of 330-660 kilometers, a region that includes a transition zone. They are formed in eclogite but are distinguished from shallow diamonds by majorite inclusions (garnet form with excess silicone). The same diamond proportion comes from the lower mantle at depths between 660 and 800 kilometers.
The diamonds are thermodynamically stable at high pressure and temperature, with phase transitions of graphite occurring at larger temperatures as pressure increases. Thus, beneath the continent it stabilizes at a temperature of 950 degrees Celsius and a pressure of 4.5 gigapascals, corresponding to a depth of 150 kilometers or more. In the subduction zone, which is cooler, it becomes stable at a temperature of 800 degrees C and a pressure of 3.5 gigapascals. At a depth of more than 240 km, a metal-nickel metal phase is present and the carbon may be dissolved in it or in the form of carbides. Thus, the deeper origins of some diamonds may reflect an unusual growth environment.
In 2018, the first natural example of an ice phase called Ice VII was found as an inclusion in diamond samples. Inclusions form at depths between 400 and 800 kilometers, straddle the upper and lower mantles, and provide evidence for water-rich liquids at this depth.
carbon source
The amount of carbon in the mantle is not well constrained, but the concentration is estimated to be 0.5 to 1 part per thousand. It has two stable isotopes, 12 C and 13 C, in a ratio of about 99: 1 with mass. This ratio has a wide range in meteorites, which implies that it may also be widespread in early Earth. It can also be altered by surface processes such as photosynthesis. Fraction is generally compared to standard sample using ratio? 13 C is expressed in parts per thousand. Common rocks of the mantle such as basalt, carbonatites and kimberlites have a ratio between -8 and -2. On the surface, organic sediments have an average of -25 while carbonates have an average of 0.
The diamond population from various sources has a distribution? 13 C which varies greatly. Peridotitic diamonds are mostly within the typical mantle range; Eclogitic diamonds have a value of -40 to 3, although the peak of the distribution is within the range of the mantle. This variability implies that they are not formed from primordial carbon (have stayed in the mantle since the Earth was formed). Rather, they are the result of tectonic processes, though (considering the age of diamond) is not necessarily the same tectonic processes that act in the present.
Formation and growth
Diamonds in the form of a mantle through a metasomatic process in which C-O-H-N-S liquids or melts dissolve minerals in rocks and replace them with new minerals. (The faint COHNS term is usually used because the exact composition is unknown.) The diamond shapes of this liquid either by oxidized carbon reduction (eg CO 2 or CO 3 ) or reduced-phase oxidation such as methane.
Using probes such as polarized light, photoluminescence and cathodoluminescence, a series of growth zones can be identified in diamonds. The pattern of characteristics in diamonds of lithosphere involves a series of nearly concentric zones with very thin oscillations in luminesens and alternating episodes where the carbon is absorbed by the liquid and then grow again. The diamond from the bottom of the lithosphere has a more irregular texture, almost polycrystalline, which reflects higher temperature and pressure and diamond transport by convection.
Carrying the surface
Geological evidence supports models in which the kimberlite magma rises at 4-20 meters per second, creating an upward path with hydraulic fracturing rocks. As the pressure decreases, the vapor phase dissolves from the magma, and this helps keep the magma fluid. On the surface, the initial eruption bursts out through the gap at high speed (over 200 meters per second). Then, at a lower pressure, the rocks are eroded, forming a pipe and producing a fragmented (breccias) rock. When the eruption is reduced, there is a pyroclastic phase and then metamorphism and hydration produce serpentinite.
In space
Although diamonds on Earth are rare, they are very common in outer space. In meteorites, about 3 percent of carbon is in the form of nanodiamond, having a diameter of several nanometers. Small enough diamonds can form in cold space because the energy of the lower surface makes them more stable than graphite. The isotope signs of some nanodiamond indicate that they form outside the Solar System in the stars.
High-pressure experiments predict that large amounts of diamonds condense from methane to "diamond rain" on icy planet Uranus and Neptune. Some extrasolar planets may be almost entirely of diamonds.
Diamonds may exist in carbon-rich stars, especially white dwarfs. One theory for the origin of carbonado, the heaviest form of diamond, is that it comes from a white dwarf or a supernova. Diamonds formed in stars may be the first mineral.
Material properties
A diamond is a transparent crystal of tetrahedrally bounded carbon atoms in a covalent (sp 3)/crystal> network lattice that crystallizes into a diamond lattice which is a variation of a face-centered cube structure. Diamonds have been adapted for many uses due to the exceptional physical properties of the material. The most notable are extreme hardness and thermal conductivity (900- 2320WÃ, Â · m -1 Ã, Â · K -1 ), as well as wide bandgap and high optical dispersion. Above 1700Ã, Â ° C ( 1973Ã, K /span> 3583Ã, Â ° F ) in a vacuum or oxygen free, the diamond turns into graphite ; in the air, the transformation begins at ~ 700Ã, Â ° C . The Diamond ignition point is 720- 800Ã, Â ° C in oxygen and 850- 1000Ã, Â ° C in the air. Natural diamonds have a density ranging from 3.15 to 3.53 g/cm 3 , with pure diamonds approaching 3.52 g/cm 3 . The chemical bonds that hold the carbon atoms in the diamond together are weaker than those in graphite. In diamonds, the bonds form an inflexible three-dimensional grid, while in graphite, the atoms are tightly bonded into sheets, which can glide easily over each other, making the overall structure weaker. In a diamond, each carbon atom is surrounded by four adjacent carbon atoms forming a tetrahedral-shaped unit. Crystal habits
Diamonds occur most often as euhedral or rounded octahedra and twin octahedra known as macles . Because the diamond crystal structure has a cubic arrangement of atoms, they have many cube-shaped, octahedron, rhombicosidodecahedron, tetrakis hexahedron or dodecahedron disdyakis. Crystals can have rounded and non-expressive sides and may be elongated. Diamonds (especially those with round crystal faces) are usually found coated with nyf , candy-like skins.
Some diamonds have opaque fibers. They are referred to as blur if the fibers grow from a clear or fibrous substrate if they occupy the entire crystal. Their colors range from yellow to green or gray, sometimes with white vaginal to gray like clouds. Their most common forms are cuboid, but they can also form octahedra, dodecahedra, macles or combined shapes. The structure is the result of many impurities with sizes between 1 and 5 microns. These diamonds may be formed in kimberlite magma and sampled from volatiles.
Diamonds can also form polycrystalline aggregates. There are attempts to classify them into groups with names such as boards, ballasts, stewartites and framesites, but no widely accepted set of criteria. Carbonado, a type in which diamond grains are sintered (fused without melting by heat and pressure applications), is black and harder than a single crystal diamond. It was never observed in volcanic rock. There are many theories for its origin, including star formations, but no consensus.
Violence
Diamonds are the hardest known natural ingredients on the Vickers scale and Mohs scale. Diamond's massive hardness relative to other materials has been known since antiquity, and is the source of its name.
The hardness diamond depends on its purity, perfection and crystal orientation: higher hardness for pure, flawless crystals oriented at & lt; 111 & gt; direction (along the longest diagonal of the cubic diamond lattice). Therefore, while it is possible to scratch some diamonds with other materials, such as boron nitride, the hardest diamonds can only be scratched by other diamonds and nanocrystalline diamond aggregates.
Diamond hardness contributes to its conformity as a gemstone. Because it can only be scratched by other diamonds, it retains its polish very well. Unlike other gems, it is perfect for everyday wear because of its resistance to scratching - may contribute to its popularity as a preferred gem in engagement or wedding rings, which are often worn on a daily basis.
The hardest natural diamonds come mostly from the Copeton and Bingara fields located in the New England region of New South Wales, Australia. These diamonds are generally small, perfect for semiperfect octahedra, and are used to polish other diamonds. Their hardness is associated with a form of crystal growth, which is a single-stage crystal growth. Most other diamonds show more evidence of several stages of growth, resulting in inclusions, defects, and aircraft defects in the crystal lattice, all of which affect its hardness. It is possible to treat ordinary diamonds under a combination of high pressure and high temperature to produce diamonds that are harder than the diamonds used in the gauge.
Somewhat associated with hardness is another mechanical characteristic toughness , which is the material's ability to withstand damage from strong impacts. The toughness of natural diamonds has been measured as 7.5-10 MPaÃ, m 1/2 . This value is good compared to other ceramic materials, but is poor compared to most engineering materials such as engineering alloys, which typically show a toughness of over 100 MPaÃ, m 1/2 . Like any material, macroscopic diamond geometry contributes to its resistance to damage. Diamonds have a field of cleavage and are therefore more fragile in some orientations than others. Diamond cutter uses this attribute to cut some stones, before faceting. "Impact of toughness" is one of the major indices for measuring the quality of synthetic industrial diamonds.
Hold the pressure
Used in so-called diamond anvil experiments to create high-pressure environments, diamonds can withstand crushing pressures of more than 600 gigapascals (6 million atmospheres).
Electrical Conductivity
Other specialized applications also exist or are being developed, including used as semiconductors: some blue diamonds are natural semiconductors, in contrast to most diamonds, which are excellent electrical insulators. The conductivity and blue color come from boron impurities. Boron replaces the carbon atoms in the diamond lattice, donating the hole into the valence band.
Substantial conductivity is generally observed in non-woven nominal diamonds grown by chemical vapor deposition. This conductivity is related to the surface-permeable hydrogen-related species, and can be removed by annealing or other surface treatments.
Surface properties
Diamonds are naturally lipophilic and hydrophobic, meaning the diamond surface can not be wet by water, but can be easily wet and retained by oil. This property can be used to extract diamonds using oil when making synthetic diamonds. However, when diamond surfaces are chemically modified with certain ions, they are expected to be so hydrophilic that they can stabilize several layers of water ice at human body temperature.
Diamond surface partially oxidized. The oxidized surface can be reduced by heat treatment under the hydrogen stream. That is, this heat treatment partially removes the oxygen-containing functional group. But the diamond (sp 3 C) is unstable against high temperatures (above about 400 ° C (752 ° F)) under atmospheric pressure. The structure gradually turns into sp 2 C above this temperature. Thus, diamonds should be reduced below this temperature.
Chemical stability
Diamonds are not very reactive. Under room temperature, the diamond does not react with any chemical reagents including strong acids and bases. The diamond surface can only be oxidized at temperatures above about 850 ° C (1,560 ° F) in the air. Diamond also reacts with a fluorine gas above about 700 ° C (1,292 ° F).
Color
Diamond has a 5.5Ã © e spacing of 5.5Ã, eV according to the ultraviolet wavelength in 225 nanometers. This means that pure diamonds must transmit visible light and appear as crystals without clear color. The color in the diamond comes from the grating defects and dirt. The diamond crystal lattice is very strong, and only the nitrogen, boron and hydrogen atoms can be put into the diamond during growth at a significant concentration (up to the percentage of atoms). The transition of nickel and cobalt metal, typically used for the growth of synthetic diamonds by high pressure high pressure techniques, has been detected in diamonds as individual atoms; maximum concentration of 0.01% for nickel and even less for cobalt. Almost all elements can be introduced to diamond by ion implantation.
Nitrogen is by far the most common impurity found in gem gems and is responsible for the yellow and brown color of the diamond. Boron is responsible for the blue color. Colors in diamonds have two additional sources: irradiation (usually by alpha particles), which causes color in green diamonds, and plastic deformation of diamond crystal lattice. Plastic deformation is the cause of color in some brown diamonds and may be pink and red. In order to increase scarcity, yellow diamonds are followed by brown, colorless, then by blue, green, black, pink, orange, purple, and red. "Black", or Carbonado, diamonds are not exactly black, but contain many dark inclusions that give the gems their dark appearance. Colored diamonds contain impurities or structural defects that cause staining, while pure or almost pure diamonds are transparent and colorless. Most diamond droppings replace carbon atoms in the crystal lattice, known as carbon defects. The most common impurities, nitrogen, cause a slight intense yellow color depending on the type and concentration of nitrogen present. Gemological Institute of America (GIA) classifies yellow and brown diamonds with low saturation as diamonds within the normal color range , and applies the rating scale of "D" (colorless) to "Z" (light yellow). Diamonds of different colors, like blue, are called fancy colors diamonds and fall under different scoring scales.
In 2008, Wittelsbach Diamond, a 35.56 carat blue diamond (7,112 g) that once belonged to the King of Spain, earned over US $ 24 million at Christie's auction. In May 2009, the 7.03 carat blue diamond (1.406 g) earned the highest price per carat ever paid for diamonds when it was sold at auction for 10.5 million Swiss francs (6.97 million euros or $ 9.5 million in time). The note, however, was beaten in the same year: a pink 5-karat pink diamond (1.0 g) sold for $ 10.8 million in Hong Kong on December 1, 2009.
Identify
Diamonds can be identified with high thermal conductivity. Their high refractive index is also indicative, but other materials have the same refractivity. Diamonds cut glass, but this does not positively identify diamonds because other materials, such as quartz, are also located above the glass on the Mohs scale and can also cut it. Diamonds can scratch other diamonds, but this can cause damage to one or both stones. Hardness tests are rarely used in practical gemology because of their potentially destructive nature. Extreme hardness and high diamond grades mean gems are usually polished slowly, using painstaking traditional techniques and greater attention to detail than with other gems; this tends to produce a very flat, highly polished aspect with a very sharp edge edge. Diamonds also have very high refractive index and high dispersion. Taken together, these factors affect the overall appearance of the polished diamond and most diamantaires still rely on the skilled use of the magnifying glass to identify the diamond "with the eye".
Industry
The diamond industry can be separated into two different categories: one dealing with grade gem diamonds and another for industrial grade diamonds. Both markets value diamonds differently.
Gem-grade diamonds
Trades of diamond gems are there. Although most gems of newly sold gems are polished, there is an established market for resale polished diamonds (eg pawnshops, auctions, jewelry stores, diamantrals, exchanges, etc.). One feature of quality gem diamond trading is its remarkable concentration: wholesale trade and diamond cutting is limited to only a few locations; In 2003, 92% of the world's diamonds were cut and polished in Surat, India. Another important center of diamond cutting and trading is the Antwerp diamond district in Belgium, where the International Gemological Institute is based, London, the Diamond District in New York City, the Diamond Exchange District in Tel Aviv, and Amsterdam. One contributing factor is the geological nature of the diamond deposits: several large main pipeline mines each account for a significant share of the market (such as the Jwaneng mine in Botswana, which is a single large mine that can generate between 12,500,000 and 15,000,000 carats (2,500 and 3,000Ã, kg) of diamonds per year). Secondary alluvial diamond deposits, on the other hand, tend to split among many different operators as they can be spread over hundreds of square kilometers (eg, alluvial deposits in Brazil).
Production and distribution of diamonds is largely consolidated in the hands of several key players, and concentrated in the traditional diamond trading center, the most important being Antwerp, where 80% of all diamonds are rough, 50% of all diamonds are cut and more than 50% of all combined rough, cut and industrial diamonds handled. This makes Antwerp the "world diamond capital" de facto. The city of Antwerp also hosts Alteres Antwerche, created in 1929 to become the first and largest diamond exchanges dedicated to rough diamonds. Another important diamond center is New York City, where nearly 80% of the world's diamonds are sold, including auction sales.
The De Beers company, as the largest diamond mining company in the world, holds a dominant position in the industry, and has done so soon after it was founded in 1888 by British imperialist Cecil Rhodes. De Beers is currently the world's largest provider of diamond production facilities (diamonds) and distribution channels for gem-quality diamonds. The Diamond Trading Company (DTC) is a subsidiary of De Beers and markets rough diamonds from a mine operated by De Beers. De Beers and its subsidiaries have mines that account for about 40% of the world's annual diamond production. For much of the 20th century over 80% of the world's rough diamonds passed through De Beers, but in 2001-2009 the figure decreased to about 45%, and by 2013 the company's market share has declined further to about 38% in terms of value and even less by volume. De Beers sold most of its diamond stocks in the late 1990s - early 2000s and the remainder was largely a stock of work (diamonds being sorted before sale). This is well documented in the media but is still little known to the general public.
As part of its reduction in impact, De Beers withdrew from buying diamonds on the open market in 1999 and stopped, at the end of 2008, buying a Russian diamond mined by Russia's largest diamond company, Alrosa. In January 2011, De Beers stated that they only sell diamonds from the following four countries: Botswana, Namibia, South Africa, and Canada. Alrosa had to suspend their sales in October 2008 due to the global energy crisis, but the company reported that it had sold rough diamonds on the open market in October 2009. In addition to Alrosa, other important diamond mining companies include BHP Billiton, the world's largest mining company; Rio Tinto Group, owner of Argyle diamond mines (100%), Diavik (60%), and Murowa (78%); and Petra Diamonds, owner of several major diamond mines in Africa.
Further down the supply chain, members of the World Federation of Diamond Bourses (WFDB) act as a medium for wholesale diamond exchange, fine and rough diamond trade. The WFDB consists of independent diamond exchanges at major cutting centers such as Tel Aviv, Antwerp, Johannesburg and other cities in the United States, 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 finance war and inhumane acts. Additional WFDB activities include sponsoring the World Diamond Congress every two years, as well as the establishment of International Diamond Council (IDC) to oversee diamond incorporation.
Once purchased by Sightholders (which is a trademark term referring to a company that has a three year supply contract with DTC), diamonds are cut and polished in preparation for sale because gems ('industrial' stones are considered a by-product of the gemstone market, they used for abrasives). Cutting and polishing rough diamonds are special skills that are concentrated in a number of locations around the world. The traditional diamond cutting centers are Antwerp, Amsterdam, Johannesburg, New York City, and Tel Aviv. Recently, diamond cutting centers have been established in China, India, Thailand, Namibia, and Botswana. Cutting centers with lower labor costs, especially Letters in Gujarat, India, deal with more smaller diamonds, while smaller numbers of larger or more valuable diamonds are more likely to be handled in Europe or North America. The recent expansion of the industry in India, using low-cost labor, has allowed smaller diamonds to be prepared as gems in larger quantities than economically feasible.
Diamonds are prepared as gems sold in the diamond exchanges called bursa . There are 28 listed diamond exchanges in the world. Exchange is the last tightest controlled step in the diamond supply chain; wholesalers and even retailers can buy many relatively small diamonds on the exchange, after which they are ready for final sale to consumers. Diamonds can be sold already set in jewelry, or sold not set ("loose"). According to Rio Tinto Group, in 2002, diamonds were produced and released to the market worth US $ 9 billion as a rough diamond, US $ 14 billion after cut and polished, US $ 28 billion in diamond jewelry wholesale, and US $ 57 Ã, in retail sales.
Cut
The mined diamond diamonds are transformed into gems through a multi-step process called "cutting". Diamonds are very hard, but also fragile and can be broken by one hit. Therefore, diamond cutting is traditionally considered a complicated procedure requiring skills, scientific knowledge, tools and experience. The ultimate goal is to produce multiformed gems in which the specific angle between aspects will optimize the diamond luster, ie white light dispersion, while the number and extent of the aspect will determine the final product's weight. The weight reduction on cuts is significant and can be of the order of 50%. Some forms may be considered, but final decisions are often determined not only by scientific considerations, but also practical. For example, diamonds may be intended for display or for wear, in rings or necklaces, selected or surrounded by other gems with specific colors and shapes. Some of them can be considered classic, such as round, pear, marquise, oval, heart and diamond arrows, etc. Some of them are specialized, manufactured by certain companies, for example, Phoenix, Cushion, Mio Sole diamond, etc.
The most time-consuming part of the cut is the initial analysis of rough stone. Need to address a large number of problems, bear a lot of responsibility, and therefore can last years in the case of unique diamonds. The following issues are considered:
- The diamond hardness and its ability to split depend heavily on crystal orientation. Therefore, the diamond crystallographic structure to be cut is analyzed using X-ray diffraction to select the optimal cutting direction.
- Most diamonds contain visible non-diamond inclusions and crystal defects. Cutter must decide which defects should be removed by cutting and which ones can be stored.
- Diamonds can be broken down by a single, well-calculated hammer blow for a sharp, fast, but risky device. Or, it can be cut with a diamond saw, which is a more reliable but boring procedure.
After the initial cut, the diamond is formed in various stages of polishing. Unlike cutting, which is a responsible but fast operation, polishing removes the material with gradual erosion and is very time consuming. Relevant techniques are well developed; it is considered a routine and can be done by a technician. After polishing, the diamond is re-examined for possible defects, either left or induced by the process. These defects are concealed through various diamond enhancement techniques, such as removal, filling, or clever stone arrangements in jewelry. The remaining non-diamond inclusions are removed through laser drilling and the resulting void filling.
Marketing
Marketing has significantly affected the image of diamonds as a valuable commodity.
N. W. Ayer & amp; Son, the advertising company maintained by De Beers in the mid-20th century, managed to revive the American diamond market. And the company creates new markets in countries where there is no previous diamond tradition. Marketing N. W. Ayer includes product placements, ads that focus 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 advertises its rival diamond products as well, but this is not a problem as De Beers dominated the diamond market throughout the 20th century. De Beers's market share slumped temporarily to second place in global markets under Alrosa after the global economic crisis of 2008, dropping to less than 29% in terms of mined rust instead of for sale. The campaign lasted for decades but was effectively discontinued in early 2011. De Beers still advertises diamonds, but the ad now mostly promotes its own brand, or licensed product line, rather than a completely "generic" diamond product. The campaign may best be captured by the slogan "diamonds are forever". The slogan is now used by De Beers Diamond Jewelers, a jewelry company that is a 50%/50% joint venture between De Beers mining company and LVMH, a luxury goods conglomerate.
Brown-colored diamonds are an important part of diamond production, and are mostly used for industrial purposes. They look worthless for jewelry (not even rated on the diamond color scale). After the development of the Argyle diamond mine in Australia in 1986, and marketing, the chocolate diamond has become an acceptable gem. The change is largely due to the numbers: the Argyle mine, with diamonds totaling 35,000,000 carats (7,000 kg) per year, produces about one-third of the global production of natural diamonds; 80% of Argyle diamonds are brown.
Industry-class diamond
Industrial diamonds are highly valued for their hardness and thermal conductivity, making many diamond gemological characteristics, such as 4 C, irrelevant for most applications. 80% of mined diamonds (equivalent to about 135,000,000 carats (27,000 kg) per year) are not suitable for use as gems and used for industry. In addition to mined diamonds, synthetic diamonds found industrial applications immediately after their discovery in the 1950s; another 570,000,000 carats (114,000 kg) of synthetic diamonds are produced annually for industrial use (in 2004, in 2014 it was 4.500 million karat (900,000 kg), 90% of which were manufactured in China). Approximately 90% of grit current grinding current is synthetic origin.
The boundaries between diamond-quality gems and industrial diamonds are not well defined and partly dependent on market conditions (for example, if demand for polished diamonds is high, some lower quality stones will be polished into low-quality gemstones or lower than sold for industrial use). In the category of industrial diamonds, there are sub-categories consisting of low-quality, mostly opaque stones, known as bort.
The use of the diamond industry has historically been associated with their hardness, which makes diamond an ideal material for cutting and grinding. As the harshest natural material known, diamonds can be used to polish, cut, or remove any material, including other diamonds. Common industrial applications of this property include diamond drills and saws, and the use of diamond powder as abrasive. The cheaper industrial grade diamonds, known as bort, with more defects and colors worse than gems, are used for that purpose. Diamonds are unsuitable for machining iron alloys at high speeds, because the carbon can be soluble in iron at high temperatures created by high-speed engines, which leads to increased wear and tear on diamond tools compared to alternatives.
Specific applications include laboratory use as containment for high-pressure experiments (see diamond anvil cells), high-performance bearings, and limited use in special windows. With the continuous advances made in synthetic diamond production, future applications become viable. The high thermal conductivity of the diamond makes it suitable as a heat sink for integrated circuits in electronics.
Mine
Approximately 130,000,000 carats (26,000 kg) of diamonds are mined annually, with a total value of nearly US $ 9 billion, and about 100,000 kg (220,000 pounds) synthesized annually.
Approximately 49% of diamonds come from Central and South Africa, although important sources of minerals have been found in Canada, India, Russia, Brazil, and Australia. They are mined from kimberlite and lamproite volcanic pipes, which can carry diamond crystals, coming from deep within the Earth where high pressure and temperature allow them to form, to the surface. Natural diamond mining and distribution are the subject of frequent controversies such as concerns over the sale of diamond diamonds or diamond conflict by African paramilitary groups. The diamond supply chain is controlled by a number of powerful businesses, and is also highly concentrated in a small number of locations around the world.
Only a small part of the diamond ore is made up of actual diamonds. The ore is destroyed, where care is required not to destroy the larger diamond, and then sorted by density. Today, the diamond is located in the diamond-rich density fraction with the help of X-ray fluorescence, after which the final sorting step is done by hand. Before the use of X-rays became commonplace, the separation was done by belt grease; diamonds have a stronger tendency to stick to fats than other minerals in the ore.
Historically, diamonds are found only in alluvial deposits in the Guntur and Krishna districts of the Krishna River delta in South India. India led the world in the production of diamonds since their discovery around the 9th century BC to the mid-18th century, but the commercial potential of these sources was exhausted at the end of the 18th century and at that time India was hindered by Brazil where diamond the first non-Indian was discovered in 1725. Today, one of India's most prominent mines is located in Panna.
The extraction of diamonds from the primary deposit (kimberlites and lamproites) began in the 1870s after the discovery of Diamond Fields in South Africa. Production has increased over time and now the total accumulation of 4,500,000,000 carats (900,000 kg) has been mined since that date. Twenty percent of that amount has been mined in the last five years, and over the past 10 years, nine new mines have begun to produce; four more are waiting to be opened soon. Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia.
In the US, diamonds have been found in Arkansas, Colorado, New Mexico, Wyoming, and Montana. In 2004, the discovery of microscopic diamonds in the US led to sampling of kimberlite pipes in January 2008 in a remote part of Montana. The Crater of Diamonds State Park in Arkansas is open to the public, and is the only mine in the world where community members can dig up diamonds.
Currently, most commercially tradable diamond deposits are in Russia (mostly in the Sakha Republic, such as Mir pipes and Udachnaya pipelines), Botswana, Australia (North and West Australia) and Democratic Republic of Congo. In 2005, Russia produced nearly a fifth of global diamond yields, according to the UK Geological Survey. Australia boasts the richest diamantiferous pipeline, with production from the Argyle diamond mine reaching a peak of 42 metric tons per year in the 1990s. There are also commercial deposits that are actively mined in the Northwest Territories of Canada and Brazil. Diamond miners continue to search the world for kimberlite and lamproite pipe containing diamonds.
Political issues
In some politically unstable African and West African countries, revolutionary groups have taken control of diamond mines, using the proceeds of diamond sales to finance their operations. The diamonds sold through this process are known as diamond conflict or blood diamond .
In response to public concerns that their diamond purchases contributed to war and human rights violations in central and western Africa, the United Nations, the diamond industry and the diamond trading countries introduced Kimberley Process in 2002. The Kimberley process aims to ensure that diamond conflicts do not become mingled with diamonds that are not controlled by the rebel group. This is done by requiring diamond-producing countries to provide evidence that the money they generate from diamond sales is not used to finance criminal or revolutionary activities. Although the Kimberley Process has been quite successful in limiting the number of conflict diamonds entering the market, some still find its way in. According to the International Diamond Manufacturers Association, conflict diamonds constitute 2-3% of all traded diamonds. Two major weaknesses still hinder the effectiveness of the Kimberley Process: (1) the relative ease of smuggling diamonds across the African border, and (2) the nature of the diamond mining violence in countries that are not in a state of technical warfare and whose diamonds are therefore considered "clean".
The Government of Canada has established a body known as the Canadian Diamond Behavior Code to help authenticate Canadian diamonds. This is a rigorous diamond tracking system and helps protect the "conflict-free" label from Canadian diamonds. Synthetics, simulants, and enhancements
Synthetic Synthetic diamonds are diamonds produced in laboratories, not diamonds mined from Earth. The use of gemology and the diamond industry has created a great demand for rough stones. This demand has been fulfilled largely by synthetic diamonds, which have been produced by various processes for more than half a century. However, in recent years it has become possible to produce quality gem-quality synthetic gems with significant size. It is possible to make colored synthetic gemstones which, at the molecular level, are identical to natural stones and are so visually similar that only a gemologist with special equipment can distinguish them.
The majority of commercially available synthetic diamonds are yellow and are produced by a process called high pressure high pressure (HPHT). Yellow color is caused by nitrogen impurities. Other colors may also be reproduced such as blue, green or pink, which are the result of the addition of boron or from irradiation after synthesis.
Another popular method for growing synthetic diamonds is chemical vapor deposition (CVD). Growth occurs under low pressure (under atmospheric pressure). This involves administering a gas mixture (typically 1 to 99 methane to hydrogen) into a chamber and splitting it into a chemically active radical in a plasma ignited by microwaves, hot filaments, arc discharges, lasers or lasers. This method is widely used for coatings, but can also produce single crystals of a size of several millimeters (see figure).
In 2010, almost all 5,000 million carats (1,000 tons) of synthetic diamonds produced per year are for industrial use. About 50% of the 133 million carats of mined diamonds annually end up in industrial use. The cost of mining companies averages $ 40 to $ 60 per carat for natural diamonds without color, while the cost of a synthetic plant averages $ 2,500 per carat for synthetic diamonds, colorless diamonds without color. However, buyers are more likely to face synthetics when looking for a luxuriously colored diamond because almost all the luxuriously colored synthetic diamonds, while only 0.01% of the natural diamond.
Simulants
Diamond simulant is a non-diamond material used to simulate the appearance of diamonds, and can be referred to as diamante. Cubic zirconia is the most common. Moissanite gemstones (silicon carbide) can be treated as a diamond simulant, although it is more expensive to produce than cubic zirconia. Both are synthetically manufactured.
Enhancements
Diamond enhancement is a special treatment performed on natural or synthetic diamonds (usually cut and polished into gems), designed to better gem stone characteristics in one or more ways. These include laser drilling to eliminate inclusions, sealant applications to fill cracks, treatments to increase the value of white diamond colors, and treatments to give a luxurious color to white diamonds.
Layers are increasingly being used to provide diamond simulants like cubic zirconia that are more "diamond-like" appearance. One such substance is diamond-like carbon - an amorphous carbon material that has some physical properties similar to a diamond. Ads indicate that such a layer will transfer some properties such as diamonds to layered stones, thereby increasing the diamond simulant. Techniques such as Raman spectroscopy should be easy to identify such treatment.
Identification
Early diamond identification tests include initial tests that rely on superior hardness of diamonds. This test is damaging, because diamonds can scratch other diamonds, and are rarely used today. In contrast, diamond identification depends on its superior thermal conductivity. Electronic thermal probes are widely used in gemological centers to separate diamonds from their imitations. The probe consists of a pair of battery-powered thermistors mounted at the ends of fine copper. One thermistor acts as a heating device while the other measures the copper edge temperature: if the stone tested is a diamond, it will conduct tip heat energy fast enough to produce a measurable temperature drop. This test takes about 2-3 seconds.
While thermal probes can separate diamonds from most of their simulants, differentiating between different types of diamonds, such as synthetic or natural, irradiated or non-irradiated, etc., require more sophisticated optical techniques. These techniques are also used for several diamond simulants, such as silicon carbide, which passed the thermal conductivity test. Optical techniques can distinguish between natural diamonds and synthetic diamonds. They can also identify most of the treated natural diamonds. The "perfect" crystals (at the atomic lattice level) are never found, so both natural and synthetic diamonds always have characteristic imperfections, arising from their crystal growth state, allowing them to be distinguished from each other.
The laboratory uses techniques such as spectroscopy, microscopy and luminescence under short wave ultraviolet light to determine the origin of diamonds. They also use custom-made instruments to help them in the identification process. Two filtering instruments are DiamondSure and DiamondView, both manufactured by DTC and marketed by GIA.
Some methods to identify synthetic diamonds can be done, depending on the production method and the color of the diamond. CVD diamonds can usually be identified by orange fluorescence. D-J colored diamonds can be screened through Diamond Spotter from the Swiss Gemmological Institute. The stones in the D-Z color range can be checked through the UV/visible DiamondSure spectrometer, a tool developed by De Beers. Similarly, natural diamonds usually have minor imperfections and deficiencies, such as the inclusion of foreign materials, which are not seen in synthetic diamonds.
Filtering devices based on diamond type detection can be used to make the difference between a natural diamond and a potentially synthetic diamond. Those with a potentially synthetic diamond require more investigation in specialized laboratories. Examples of commercial screening devices are D-Screen (WTOCD/HRD Antwerp) and Alpha Diamond Analyzer (Bruker/HRD Antwerp).
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Stolen diamond
Sometimes big thefts happen. In February 2013, armed robbers staged an attack at Brussels Airport and escaped with gems estimated to be worth $ 50 million (£ 32 million; 37 million euros). The gang broke through the guardrail and raided the cargo hold from a Swiss-bound plane. The gang has been arrested and a large amount of cash and diamonds recovered.
Identification of stolen diamonds presents a set of difficult problems. Rough diamonds will have a distinctive shape depending on whether their source is mine or from alluvial environments such as beaches or rivers - alluvial diamonds have finer surfaces than mined ones. Determining the origin of cut stone and polish is much more complex.
The Kimberley process was developed to monitor the rough diamond trade and prevent them from being used to fund violence. Before exporting, rough diamonds are certified by the government of the country of origin. Some countries, such as Venezuela, are not parties to the agreement. The Kimberley process does not apply to the sale of rough local diamonds in a country.
Source of the article : Wikipedia
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