Diamond
In mineralogy, diamond is an allotrope of carbon in which the carbon atoms are arranged in a variant of the so-called face-centered cubic crystal structure. Diamond is the second most stable form of carbon, after graphite; however, the conversion rate from diamond to graphite is negligible at ambient conditions. Diamond is specifically renowned as a material with superlative physical characteristics, many of which derive from the strong covalent bond between its atoms. In particular, diamond has the highest hardness and thermal conductivity of all materials known to man. These properties determine that the main industrial application of diamond is in cutting and polishing tools, among other applications.
Diamond is one of the most valuable minerals in the world due to its physical and optical characteristics. Due to its extremely rigid crystal structure, it can be contaminated by few types of impurities, such as boron and nitrogen. Combined with their high transparency (corresponding to a wide bandgap of 5.5 eV), this results in the clear, colorless appearance of most natural diamonds. Small amounts of defects or impurities (approximately one part per million) induce a diamond color of blue (boron), yellow (nitrogen), brown (crystalline defects), green, violet, pink, black, orange, or red. Diamond also has relatively high refractive dispersion, that is, the property of dispersing light of different colors, resulting in its characteristic luster. Its excellent optical and mechanical properties, combined with efficient marketing, make diamond the most popular gem.
Most natural diamonds form under conditions of extreme pressure and temperature existing at depths of 140 km to 190 km in the Earth's mantle. Carbon-containing minerals provide the carbon source, and growth occurs in periods of 1 to 3.3 billion years, which corresponds to approximately 25 to 75% of the age of the Earth. Diamonds are carried near the Earth's surface through deep volcanic eruptions by magma, which cools into igneous rocks known as kimberlites and lamproites. Diamonds can also be produced synthetically in a high-pressure, high-temperature process that roughly simulates conditions in the Earth's mantle. An alternative, and completely different technique, is chemical vapor deposition. Some materials other than diamond, such as cubic zirconia and silicon carbide, are often called diamond simulants, because they resemble diamond in appearance and many properties. Special gemological techniques have been developed to distinguish natural from synthetic diamonds and diamond simulants.
History
The name diamonds derives from the ancient Greek ἀδάμας (adámas), “own”, “unchangeable”, “unbreakable, indomitable”, from ἀ- (a-), "without" + δαμάω (damáō), "I rule, I dome". However, it is thought that the diamonds were recognized and first mined in India, where significant alluvial deposits of such stone may have been found many centuries ago along the Penner, Krishna and Godavari rivers. It is considered proven that diamonds were known in India for at least 3,000 years, and it is conjectured that they were known as early as 6,000 years ago.
Diamonds have been treasured as gems since their use as religious icons in ancient India. Their use in engraving tools also dates back to earliest human history. The popularity of diamonds has been growing since the 19th century due to its increasing supply, better cutting and polishing techniques, growth in the world economy, and innovative and successful advertising campaigns.
In 1813 Humphry Davy used a lens to focus the sun's rays onto a diamond in an oxygen atmosphere and showed that the only product of combustion was carbon dioxide, proving that diamond was composed of carbon. He later showed that, in an atmosphere devoid of oxygen, diamond turns into graphite.
The most familiar use of diamonds today is as gemstones worn for adornment, a use that dates back to ancient times. The dispersion of white light in spectral colors is the primary gemological characteristic of diamond gems. In the XX century, experts in the field of gemology have developed methods for classifying diamonds and other gems, based on the most important characteristics of its gem value. The four characteristics, known informally as the four Cs, developed by the GIA, are now commonly used as basic descriptors for diamonds: these are carat, cut, colour and clarity (weight, size, color and purity).
The Cullinan, or Star of the South, is the largest diamond found in all of known history. Its value was incalculable, to such an extent that it had to be cut into several fragments. There are many diamonds in the world, but very few that can compare to Cullinan, the pink panther of the real world. Extracted from a mine owned by Sir Thomas Cullinan 40 kilometers from Pretoria, South Africa, it weighed in the rough 3,106 carats (621 grams) and was given as a birthday present to British King Edward VII.
Material properties
A diamond is a transparent crystal of tetrahedrally bonded (sp3) carbon atoms that crystallizes in the diamond lattice, which is a variation of the face-centered cubic structure. Diamonds have been adapted for many uses due to their unique physical characteristics. Most notable are its extreme hardness and thermal conductivity (900–2,320 W/(m K)), as well as the wide bandgap and high optical dispersion. Above 1,700 °C (1,973 K / 3,583 °F) in a vacuum or in an oxygen-free atmosphere, diamond turns into graphite; in air the transformation begins at approximately 700 °C. Diamonds existing in nature have a density ranging from 3.15–3.53 g/cm³, with very pure diamonds generally extremely close to 3.52 g/cm³.
Hardness
Diamond is the hardest natural material known to date (although studies began in 2009 that seem to show that lonsdaleite is 58% harder) where hardness is defined as resistance to scratching. Diamond has a hardness of 10 (the highest) on the Mohs scale of mineral hardness. Diamond's hardness has been known since ancient times and is the source of its name.
The hardest natural diamonds in the world are found in the Copeton and Bingara fields, located in the New England area of New South Wales, Australia. They were called can-ni-faire ("nothing can be done with them"—a combination of English "can" = power, Italian "ni& #34; = not and French "faire" = to do) by cutters in Antwerp when they began arriving in quantities from Australia in the 1870s. These diamonds are generally small, perfect to semi-perfect octahedrons, and are used to polish other diamonds. Its hardness is associated with the way the crystal grows, which is in a single stage. Most other diamonds show more evidence of multiple growth stages, producing inclusions, faults, and flaw planes in the crystal lattice, all of which affect their hardness. Regular diamonds can be treated under a combination of pressure and high temperature to produce diamonds that are harder than diamonds used in hardness devices.
The hardness of diamonds contributes to their fitness as a gem. Because they can only be scratched by other diamonds, they hold their polish extremely well. Unlike other gemstones, they are well suited to everyday wear due to their scratch resistance—perhaps this contributes to their popularity as the gem of choice in engagement rings and wedding rings, which have often been worn every day for decades.
The industrial use of diamonds has historically been associated with its hardness; this property makes diamond the ideal material for cutting and polishing tools. As the hardest known natural material, diamond can be used to polish, cut, or abrade any material, including other diamonds. Common industrial adaptations of this skill include drill bits and saws, and the use of diamond dust as an abrasive. Less expensive industrial grade diamonds, known as bort, with many flaws and poorer color than gems, are used for such purposes.
Diamond is not suitable for high-speed ferrous alloy machining, since carbon is soluble in iron at the high temperatures created by high-speed machining, leading to increased wear on diamond tools when used. compare with alternatives.
These substances can scratch diamond:
- Some diamonds are tougher than others.
- The nanocrystalline aggregates of diamonds produced by high pressure treatment and high graphite or fuller temperature (C60).
- Nitride of cubic boro (Borazón)
- A hexagonal shape of the diamond called lonsdaleite, which has been theoretically predicted to be 58% stronger than the diamond.
Electrical conductivity
Other specialized applications also exist or are being developed, including their use as semiconductors: some blue diamonds are naturally occurring semiconductors, in contrast to most other diamonds, which are excellent electrical insulators. The blue color and conductivity originate from the boron impurity. Boron replaces carbon atoms in the diamond lattice, donating a hole in the valence band.
Substantial conductivity is commonly observed in nominally undoped diamonds, which have grown by chemical vapor deposition. This conductivity is associated with species related to hydrogen adsorbed on the surface, and can be removed by annealing or other surface treatments.
Tenacity
Toughness refers to the material's ability to resist breaking under strong impact. The toughness of natural diamond has been measured as 2.0 MPa m1/2, and the critical stress intensity factor is 3.4 MN m−3/2. These values are high compared to other gems, but low compared to most engineering materials. As with any material, the microscopic geometry of a diamond contributes to its resistance to fracture. Diamond has a fracture plane and hence is more brittle in some orientations than others. Diamond cutters use this attribute to break some stones, prior to faceting.
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Colour
Diamond has a broad bandgap of 5.5 eV (or 225 nm) spanning the entire visible spectrum, which means that pure diamond should transmit visible light and appear as a clear, colorless crystal. The origin of the colors in the diamond is in network defects and impurities. Most impurities in diamonds consist of the replacement of a carbon atom in the crystal lattice. The most common impurity, nitrogen, causes a light to intense yellow coloration, depending on the type and concentration of nitrogen present. Low yellow and brown saturation are classified by the Gemological Institute of America (GIA) as diamonds in the normal range color, and applies a graduation scale from 'D' (colorless) to 'Z' (slightly yellow). Nitrogen is by far the most common impurity found in diamond gems and is responsible for the yellow and brown in diamonds (see also: nitrogen-vacancy center). Boron is responsible for the blue-gray color. Diamonds of a different color, such as blue, are called 'fancy-colored' diamonds, and fall under a different grading scale.
The transition metals Ni and Co, which are commonly used for synthetic diamond growth by high pressure and high temperature techniques, have been detected in diamonds as single atoms, however the maximum concentration is 0.01 % for Ni, and even much less for Co. Note, however, that virtually any element can be introduced into diamond by ion implantation.
Color in diamonds has two additional sources: irradiation (usually by alpha particles) which causes color in green diamonds, and physical deformations of the diamond crystal known as plastic deformations. Plastic deformation is the cause of color in certain brown diamonds and perhaps some pink and red diamonds. In order of rarity, colorless diamonds, by far the most common, are followed by yellow and brown, then blue., greens, blacks, translucent whites, pinks, violets, oranges, purples, and the rarest, reds. "Black" diamonds are diamonds that are not truly black, but contain numerous dark inclusions that give the color gem a dark appearance.
The best known and most valuable black diamond is the "Black Orlov Diamond", although it is more valuable for its history than for being black. (Not to be confused with the Oslov Diamond).
In 2008, the Wittelsbach Diamond, a 35.56-carat (7.11 g) blue diamond believed to have belonged to the King and Queen of Spain, fetched more than $24 million at auction from Christie's. In 2009, a 7.03-carat (1.41g) blue diamond fetched the highest price per carat ever paid for a diamond, when it sold at auction for 10.5 million francs Swiss (6.97 million Euros or US$9.5 million at the time) which was well in excess of US$1.3 million per carat.
Identification
Diamonds can be identified by their high thermal conductivity. Its 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, are also found on the Mohs scale on glass and can cut glass as well. Diamonds easily scratch other diamonds, but this damages both diamonds.
There are physical methods for diamond identification, such as the use of heavy liquids; It is about, using the density of the diamond as a criterion, immersing the sample in a solution of methylene iodide, in which the gem will float or sink whether it is a diamond or not.
A few years ago devices were manufactured that use the thermal conductivity of diamond to distinguish it from other transparent gems. At first they were very useful, especially for those who did not have gemological knowledge, since simply by touching the gem with these devices it was possible to determine if that gem was a diamond or not. But with the advent of moissanite, another new imitation of diamond, which has a thermal conductivity very similar to that of diamond, the reliability of these devices was called into question.
There are also methods of direct observation to identify a diamond. Gemological microscopes allow us to observe the internal inclusions of the gem under study, and an expert can determine which inclusions are characteristic of a diamond and which are not. Transparency is another characteristic of the diamond, being less transparent than some of its imitations.
Natural history
Natural diamond formation requires very specific conditions—exposure of carbon-bearing materials to high pressure, ranging from 45 to 60 kilobars— although diamonds occasionally crystallize at depths of 300-400 km, but at a range of comparatively low temperature ranging from about 900-1300 °C. These conditions are found in two places on Earth; in the mantle of the lithosphere under relatively stable continental plates, and at the site of meteorite impact.
Formation in cratons
The conditions for diamond formation to occur in the mantle of the lithosphere occur at considerable depth, corresponding to the aforementioned temperature and pressure requirements. These depths are estimated to be between 140 and 190 km,
The rate at which temperature changes with increasing depth in the Earth varies greatly in different parts of the Earth. In particular, under oceanic plates, the temperature rises more rapidly with depth, beyond the range required for diamond formation at the required depth. The right combination of temperature and pressure is only found in the thick, old, and thick parts. stable continental plates, where there are regions of lithosphere known as cratons. A long stay in the cratonic lithosphere allows diamond crystals to grow even larger.
Through carbon isotopic composition studies (similar to the methodology used in radiocarbon dating, except with the stable isotopes C-12 and C-13), the carbon in diamonds has been found to come from both sources organic as inorganic. Some diamonds, known as harzburtigics, are formed from inorganic carbon originally found deep in the Earth's mantle. In contrast, eclogitic diamonds contain organic carbon from organic debris that has been pulled down from the surface of the Earth's crust through subduction (see plate tectonics) before being transformed into diamond. These two different sources of carbon have different reasons 13C:12C measurable. Diamonds that have reached the Earth's surface are generally quite old, ranging from 1 billion to 3.3 billion years old. This is from 22% to 73% of the age of the Earth.
Diamonds most often occur as eudranal or rounded octahedrons and twin octahedrons called twins. As the diamond crystal structure has a cubic arrangement of atoms, they have many facets that belong to a cube, octahedron, rhombicosidodecahedron, tetrakishexahedron, or hexakisoctahedron. The crystals can be rounded and the inexpressive edges can be elongated. They are sometimes found grown together or forming "twinned" double crystals; on the surfaces of the octahedron. These different shapes and habits of diamonds result from different external circumstances. Diamonds (especially those with rounded crystal faces) are commonly found encased in nyf, an opaque, rubbery skin.
Formation in meteorite impact craters
Diamonds can also form in other high-pressure natural events. Very small diamonds, known as microdiamonds or nanodiamonds, have been found in meteorite impact craters. Although in the Popigai Crater in Siberia the diamonds reach a size between 0.5 to 2 mm with some specimens of 10mm. It is considered to be the world's largest deposit of impact diamonds. Such impact events create shock zones of high pressure and temperature, ideal for diamond formation. Impact-type microdiamonds can be used as an indicator of ancient impact craters. Some of these diamonds have hexagonal packing (EH), Lonsdaleite, unlike the common ones that have a cubic packing (EC).
Alien Formation
Not all diamonds found on Earth originated here. A type of diamond called carbonate diamond, which is found in South America and Africa, may have been deposited there via an asteroid impact (not formed by the impact) about 3 billion years ago. These diamonds may have formed in the interstellar medium, but as of 2008, there was no scientific consensus about how carbonate diamonds originated.
Presolar grains in many meteorites found on Earth contain nanodiamonds of extraterrestrial origin, probably formed in supernovae. Scientific evidence indicates that white dwarf stars have a core of crystallized carbon and oxygen. The largest of these found in the universe so far, BPM 37093, is located 50 light-years away, in the constellation Centaurus. A press release from the Harvard-Smithsonian Center for Astrophysics described the 2,500-mile-diameter stellar core as diamond. Known as Lucy, after the song "Lucy in the Sky with Diamonds" ("Lucy in the sky with diamonds"), by The Beatles.
Arrival to the surface
Diamond-bearing rock is brought close to the surface through deep-sourced volcanic eruptions. The magma for such a volcano must originate at a depth where diamonds can be formed—150 km or more (three times or more the depth of the magma source for most volcanoes). This is something that happens relatively rarely. The vents contain material that was transported to the surface by volcanic action, but was not ejected before the volcanic activity ceased. During the eruption, these vents are open to the surface, resulting in open circulation; Many xenoliths from superficial rocks, and even wood and/or fossils, have been found in the chimneys. Diamond-bearing volcanic vents are closely related to the oldest and coldest regions of the continental crust (cratons). This is because cratons are very thick, and their lithospheric mantle extends to depths great enough that diamonds are stable. Not all smokestacks contain diamonds, and even fewer contain enough diamonds to make mining economically viable.
The magma in volcanic vents is generally of one of two characteristic types, cooling into igneous rock known as either kimberlite or lamproite. The magma itself does not contain diamonds; however, it acts as an elevator that carries rocks formed at depth (xenoliths), minerals (xenocrysts), and fluids upwards. These rocks are characteristically rich in magnesium-rich olivine, pyroxene, and amphibole minerals that are often altered to serpentine by heat and fluids during and after the eruption. Certain indicator minerals typically occur in diamondiferous kimberlites, and are used as mineralogical tracers by prospectors, who follow indicator tracks back to the volcanic vent that may contain diamonds. These minerals are rich in chromium (Cr) or titanium (Ti), elements that impart brilliant colors to the minerals. The most common indicator minerals are chromian garnets (usually bright red Cr pyrope and green garnets of the ugrandite series), eclogitic garnets, orange Ti pyrope, high Cr red spinels, dark chromite, bright green Cr diopside, glassy green olivine, black picroilmenite, and magnetite. Kimberlite deposits are known as blue soil, from the deeply serpentinized parts of the deposits, or as yellow soil, from the smectite clay near the soil and weathered carbonate and rusty part.
Once diamonds have been transported to the surface by magma in a volcanic vent, they can be eroded out and distributed over a large area. A volcanic vent containing diamonds is known as a primary source of diamonds. Secondary sources of diamonds include all areas where there are significant numbers of diamonds, eroded from their kimberlite or lamproite matrix, and accumulated by water or wind action. These include alluvial deposits and existing deposits on existing and ancient coastlines, where diamonds tend to accumulate due to their similar size and density. Diamonds have also rarely been found in deposits left behind by glaciers (notably in Wisconsin and Indiana); however, in contrast to alluvial deposits, glacial deposits are minor and therefore not viable commercial sources of diamond.
Commercial markets
The diamond industry can be separated into two basically distinct categories: one relating to gem-grade diamonds, and another for industrial-grade diamonds. Although there is a large trade in both types of diamonds, the two markets operate in drastically different and different ways.
Gems
There is a large trade in gem grade diamonds. Unlike precious metals, such as gold or platinum, gemstone diamonds are not traded as a commodity. Contrary to popular belief, there is a well-established market for the resale of polished diamonds and brilliant cut diamonds. A remarkable aspect of the gem-quality diamond trade is its very high concentration: global trade and diamond cutting is limited to only a few locations. 92% of diamond cuts in 2003 were in Surat, Gujarat, India. Other major diamond cutting and trading centers include Antwerp, London, New York, Tel Aviv, and Amsterdam. A single company—De Beers—controls a significant proportion of the diamond trade. They are based in Johannesburg, South Africa and in London, England. One contributing factor is the geological nature of the diamond deposits: some large primary kimberlite pipe mines contribute significant market shares (such as the Jwaneng diamond mine in Botswana, which is a large deposit operated by De Beers that can produce between 12.5 and 15 million carats of diamonds per year), while secondary alluvial deposits tend to be fragmented among different types of operators, as they can be dispersed over several hundred square kilometers (for example, alluvial deposits in Brazil).
Diamond production and distribution is largely entrenched in the hands of a few key players, and concentrated in traditional diamond exchange centers. Being the most important, Antwerp, where 80% of rough diamonds, 50% of all cut diamonds and more than 50% of rough, cut and industrial diamonds combined are handled. This makes Antwerp the "capital diamond world" 'de facto'. However, New York, along with the rest of the United States, is where approximately 80% of the world's diamonds are sold, including auction sales. Likewise, the largest diamonds and most unusual rough shapes also end up in New York. The De Beers company, as the largest diamond miner in the world, maintains a clearly dominant position in the industry, and has done so since its inception. founded in 1888 by British imperialist Cecil Rhodes. De Beers owns or controls a significant proportion of the world's rough diamond production facilities (mines) and distribution channels for gem-quality diamonds. The company and its subsidiaries own mines that produce nearly 40 percent of the world's annual diamond production. At one time it was thought that more than 80% of the world's production of rough diamonds passed through the Diamond Trading Company (DTC, a subsidiary of De Beers) in London, but the figure is currently estimated at approximately 40 percent. De Beers sold a vast majority of its diamond reserves in the late 1990s - early 2000s with the remainder representing mainly working inventory (diamonds being ordered prior to sale). This was well documented in the press but remains little known to the general public.
De Beer's diamond advertising campaign is regarded as one of the most successful and innovative campaigns in history. N.W. Ayer & Son, the advertising firm retained by De Beers in the mid-XX century, succeeded in reviving the American diamond market and opened new markets, even in countries where there had not been a tradition of diamonds. The multifaceted advertising campaign of N.W. Ayer included advertising by placement, advertising the diamond itself, rather than the De Beers brand, and building partnerships with celebrities and royalty. This coordinated campaign spanned decades and continues today: perhaps best captured by the catchphrase: "a diamond is forever" (a diamond is forever).
Below the supply chain, members of the World Federation of Diamond Exchanges (WFDB) act as a conduit for the global diamond exchange, trading both polished and rough diamonds. The WFDB consists of independent diamond exchanges in 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 trafficking in diamonds used to fund war and inhumane acts. Additional activities of the WFDB also include the promotion of the World Diamond Congress every two years, as well as the establishment of the International Diamond Council (IDC) to oversee the grading of diamonds.
Industrial Grade
The market for industrial grade diamonds operates very differently from its ornamental counterpart. Industrial diamonds are valued largely for their hardness and thermal conductivity, making some of the gemological characteristics of diamonds, such as clarity and color, irrelevant for most applications. This helps explain why 80% of the diamonds mined (equal to approximately 100 million carats, or 20,000 kg annually), unfit for use as precious stones, are destined for industrial use. In addition to mined diamonds, synthetic diamonds found industrial applications almost immediately after their invention in the 1950s; Another 3 billion carats (600 metric tons) of synthetic diamonds are produced annually for industrial use. Currently, approximately 90% of the abrasive material in diamond sandpaper is of synthetic origin.
The dominant industrial use of diamonds is cutting, drilling, sanding and polishing. Most uses of diamonds in these technologies do not require large diamonds; indeed, most diamonds that are of gem quality, except for their small size, can find industrial use. Diamonds are embedded in the tip of drills or saw blades, or scattered in a powder for use in sanding and polishing applications. Some specialized applications include use in laboratories as a container for high-pressure experiments, high-performance bearings, and limited use in specialized windows.
With the continued advances made in the production of synthetic diamonds, future applications are becoming feasible. Much excitement is being generated about the possible use of diamond as a semiconductor suitable for building microchips, or the use of diamond as a heatsink in electronics, although in the past in this branch of technology it was widely used in the manufacture of cartridge styli. the turntables.
The boundary between gem-quality diamonds and industrial diamonds is poorly defined, and partly depends on market conditions (for example, if demand for polished diamonds is high, some suitable stones will be polished into small gems or of low quality instead of being sold for industrial use). Within the category of industrial diamonds, there is a subcategory that comprises the lower quality stones, mainly opaque stones, which are known as bort or 'boart'.
Supply Chain
Approximately 130 million carats (26,000 kg) are mined annually, with a total value close to USD $9 billion, and approximately 100,000 kg are synthesized annually.
About 49% of diamonds come from central and southern Africa, although significant sources of the mineral have been discovered in Canada, India, Russia, Brazil and Australia. They are mined for kimberlite and lamproite present in volcanic pipes, which can transport diamond crystals -originating in the depths of the Earth where high pressures and temperatures allow them to form- to the surface. The mining and distribution of natural diamonds are a frequent source of controversy, such as concerns about the sale of "blood diamonds" by African paramilitary groups. The diamond supply chain is controlled by a limited number of powerful businesses, and is also highly concentrated in a small number of locations around the world (see figure).
Mining, sourcing and production
Only a very small fraction of diamond ore consists of actual diamonds. The ore is crushed, a process during which care is taken not to destroy the largest diamonds, and then they are sorted by density. Today, diamonds are located in the diamond-rich density fraction with the aid of X-ray fluorescence, after which the final sorting steps are done by hand. Before the use of X-rays became common, separation was done with belts of fat; diamonds have a stronger tendency to stick to grease than the other minerals in the sample.
Historically, diamonds were found only in alluvial deposits in southern India. India led the world in diamond production from the time of its discovery, around the IX B.C. to mid-century XVIII d. but the commercial potential of these fonts had been exhausted by the late 18th century, and at that time, India was dwarfed by Brazil, where the first non-Indian diamonds were found in 1725.
Diamond production from primary deposits (kimberlites and lamproites) began only in the 1870s, after the discovery of diamond fields in the Republic of South Africa. Production has increased over time, and has now been mined a cumulative total of 4.5 billion carats to date. Interesting is the fact that 20% of that amount has been mined in the last 5 years alone, and during the last ten years, 9 new mines have started production, while 4 more are waiting to be opened soon. Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia.
In the United States, diamonds have been found in Arkansas, Colorado, and Montana. In 2004, the discovery of a microscopic diamond in the United States led to the rough sampling of kimberlite pipes in a remote location from Montana.
Today, most of the commercially viable diamond deposits are in Russia (mainly in Yakutia, for example the Mir mine and the Udachnaya mine), Botswana, Australia (north and west) and the Democratic Republic of the Congo.
In 2005, Russia produced nearly a fifth of global diamond production, according to reports by the British Geological Survey. Australia has the richest diamond pipes, with production reaching peak levels of 42 MT per year in the 1990s.
There are also commercial deposits being actively mined in Canada's Northwest Territories, and in Brazil. Diamond prospectors continue to search the globe for kimberlite and lamproite pipes that contain diamonds.
Controversial sources
In some of the most politically unstable West and Central African countries, revolutionary groups have seized control of the mines, using the proceeds from diamond sales to finance their operations. Diamonds sold through this process are known as "conflict diamonds" or "blood diamonds". Large diamond-trading corporations continue to finance and fuel these conflicts by doing business with armed groups. In response to public concern that their diamond purchases may be contributing to war and human rights violations in West and Central Africa, the United Nations, the diamond industry, and diamond trading nations introduced the Kimberley Process in 2002. The Kimberley Process aims to ensure that conflict diamonds are not intermingled with diamonds controlled by such rebel groups. This is accomplished by requiring diamond-producing countries to provide proof that the money they make from diamond sales is not used to finance 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 there. Between 2% and 3% of the diamonds traded today are potentially conflict diamonds. Two major flaws still limit the effectiveness of the Kimberley Process:
(1) the relative ease of smuggling diamonds across African borders, and
(2) the violent nature of diamond mining in nations that are not technically in a state of war, and whose diamonds are therefore considered "clean".
The Canadian government has established a body known as the Canadian Diamond Code to help authenticate Canadian diamonds. This is a very rigorous diamond surveillance system, and helps protect the "conflict-free" of Canadian diamonds.
Distribution
The Diamond Trading Company (DTC) is a subsidiary of De Beers, and trades rough diamonds from De Beers-operated mines (it stopped buying diamonds on the open market in 1999, and stopped buying Russian diamonds mined by the De Beers Russian company Alrosa in late 2008. Alrosa successfully appealed against a European court and will restart sales in May 2009).
Once purchased by Sightholders (which is a proprietary term, referring to companies that have a three-year supply contract with DTC), diamonds are cut and polished in preparation for being sold as precious gems. The cutting and polishing of rough diamonds is a specialized work that is concentrated in a limited number of locations around the world. The traditional diamond cutting centers are Antwerp, Amsterdam, Johannesburg, New York and Tel Aviv. Recently, diamond cutting centers have been established in China, India, Thailand, Namibia and Botswana. Cutting centers with lower labor costs, notably Surat in Gujarat, India, handle large numbers of low-carat diamonds, while smaller amounts of the larger or more valuable diamonds tend to be handled in Europe or North America.. The recent expansion of this industry in India, employing cheap labor, has allowed smaller diamonds to be prepared into gems in larger quantities than was previously economically feasible.
Diamonds that have been prepared as precious gems are sold at diamond exchange centers known as "exchanges". There are 26 registered diamond bags in the world. The bags are the last step in the tightly controlled diamond supply chain, large wholesalers and even retailers can purchase relatively small amounts of diamonds in the bags, after which they are prepared for shipment. final sale to the consumer. Diamonds can be sold already set in jewelry, or sold unset. According to the Rio Tinto Group, in 2002 diamonds produced and released to the market were valued at US$9 billion, as rough diamonds, US$14 billion after cut and polished, US$28 billion in wholesale diamond jewelry, and $57 billion in storefront sales.
Synthetics, simulants and enhancements
Synthetics
Synthetic diamonds are diamond crystals that are manufactured in a laboratory, in contrast to natural diamonds that form naturally underground. The gemological and industrial uses of diamond have created a great demand for rough stones, this demand has been met in large part by synthetic diamonds for more than half a century; but basically for industrial use, not for the jewelry market. The processes for the manufacture of this type of gem are diverse, such as CVD and HTHP. Currently, they are beginning to be marketed for the costume jewelery sector and certain types of jewelry stores, an example of which is the well-known brand Swarovski. On the other hand, it should be remembered that they are currently easily detectable by a gemologist since natural diamonds have anomalous birefringence and synthetic diamonds do not. The same occurs with phosphorescence since practically all HPHT-type synthetics have this characteristic, while natural diamonds almost in their entirety lack this feature. Without a doubt, and for the consumer, it is good to know that a synthetic diamond is not the same as a natural one, the jeweler being obliged to indicate in the gemological certificate that it is a "synthetic diamond".
Most commercially available synthetic diamonds are yellow in color, and are produced by processes called High Pressure High Temperature (HTHP). The yellow color is caused by nitrogen impurities. Other colors can also be reproduced, such as blue, green, or pink, which result from the addition of boron or from irradiation after synthesis.
Another popular method of growing synthetic diamond is chemical vapor deposition (CVD). Growth takes place at low pressure (less than atmospheric pressure). It involves feeding a mixture of gases (typically 1:99 methane:hydrogen) into a chamber and breaking them down by the action of chemically active radicals in a plasma initiated by microwave, hot filament, electric discharge, welding torch, or laser. This method is used mainly for coatings, but can also produce individual crystals a few millimeters in size (see image).
Currently, the annual production of gem-quality synthetic diamonds is only a few thousand carats, while the total production of natural diamonds is around 120 million carats. Despite this fact, a consumer often finds synthetic diamonds when looking for a fancy color diamond, because almost all synthetic diamonds are fancy color, while only 0.01% of natural diamonds are fancy color. The production of larger synthetic diamonds threatens the business model of the diamond industry. The ultimate effect of the rapid availability of low-cost gem-quality diamonds in the future is difficult to predict.
Imitations
A rhinestone is defined as a material other than diamond that is used to simulate the appearance of a diamond. The gems that imitate the diamond are usually referred to as "diamonds", dry, although they are properly "rhinestones"; they are sometimes called "diamond simulants" because of the semantic tracing of English. The most familiar imitation diamond to most consumers is cubic zirconia. The popular gemstone moissanite (silicon carbide) is often treated like an imitation diamond, even though it is a gem in its own right. Although moissanite is similar in appearance to diamond, its main disadvantage as a diamond simulant is that cubic zirconia is much cheaper and almost as convincing. Both cubic zirconia and moissanite are produced synthetically.
Improvements
Diamond enhancements are specific treatments performed on natural or synthetic diamonds (usually those already cut and polished into a gem), that are designed to enhance the gemological characteristics of the stone in one or more ways. These include laser drilling to remove inclusions, application of sealants to fill fissures, treatment to improve the color grade of a white diamond, and treatments to give fancy color to a white diamond.
Coatings are being used more to give diamond simulants, such as cubic zirconia, a more 'diamond-like' appearance. One such substance is diamond carbon—an amorphous carbonaceous material that has some physical properties similar to those of diamonds. Publicity suggests that such a coating could transfer some of these diamond-like properties to the coated stone, with the consequence of improving the diamond simulant. However, modern techniques such as Raman spectroscopy make it easy to identify this treatment.
Identification
It has been suggested that an annealing process has been able to convert synthetic diamonds, typically brown (CVDs), into colorless diamonds, and that these diamonds, after being submitted for identification in diamond jewelry, were not identified as different from diamonds. natural diamonds. Such listings are often made for new synthetic, simulant, and treated stones, so it is important to validate how the stones were shipped for identification.
Properly trained and equipped gemologists can distinguish between natural diamonds and synthetic diamonds. They can also identify the wide variety of treated natural diamonds, two exceptions being a small minority of Type II HPHT-treated diamonds (diamonds of this type are usually brown, and through the aforementioned HPHT process what is done is a physical process which allows the diamond to get very high color, from D to H colors), and some artificially irradiated green diamonds; These natural diamonds are mostly found in Africa and are easy to spot. No "perfect" (at the atomic crystal lattice level), so both natural and synthetic diamonds always have characteristic imperfections, which arise from the circumstances of crystal growth, which allow them to be distinguished from each other.
Labs use techniques such as spectroscopy, microscopy, and luminescence under short ultraviolet light to determine the origin of a diamond. They also use specially designed machines to help them in the identification process. Two of these machines are the "DiamondSure" and the "DiamondView", both produced by the DTC and marketed by the GIA.
Some methods can be performed to identify synthetic diamonds, depending on the production method and the color of the diamond. CVD diamonds are usually identified by a red fluorescence. Diamonds colored C-J can be detected through the Swiss Gemmological Institute's Diamond Spotter. Stones in the D-Z color range can be examined through the DiamondSure UV/visible spectrometer >, a tool developed by De Beers. Similarly, natural diamonds often have minor blemishes and flaws, such as inclusions of foreign material, not seen in synthetic diamonds.
Symbols
Tradition attributed to the diamond in other times wonderful virtues against poisons, plague, panic terrors, insomnia, prestige and enchantments. He calmed the anger and preserved the love between the spouses, which gave rise to the name stone of reconciliation. A talismanic property was also attributed to it when under its favorable aspect, or when under the planet Mars, the figure of this god or of Hercules killing the hydra was engraved on it, to always ensure victory to the one who carried it, whatever the number. of his enemies.
It went to the extreme of believing that diamonds engendered others, and Ruens tells us that a princess of Luxembourg had hereditary diamonds that produced others at certain times. In iconological language, the diamond is the symbol of constancy, strength, innocence and other heroic virtues.