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Prong, Bezel, and Channel. Prong settings are the most popular setting for diamond jewelry. In bezel settings the diamond or gemstone is completely surrounded by a rim of metal, which can be molded into any shape to accommodate the stone.
Used to set earrings, necklaces, bracelets, and rings, bezel settings can have open or closed backs, and generally can be molded to allow a lot of light to pass through.
Channel settings set the stones right next to each other with no metal separating them. This setting is mostly used in wedding and anniversary bands.
The outer ridge is then worked over the edges of the stones to create a smooth exterior surface. This also protects the girdle area of the stone.
About a third of all diamonds will glow under ultraviolet light, usually a blue color which may be noticeable under a black light or strong sunlight.
Other colors diamonds can fluoresce are green , yellow , and red but are very rare and are sometimes a combination of the colors such as blue-green or orange.
Some diamonds with "very strong" fluorescence can have a "milky" or "oily" look to them, but they are also very rare and are termed "overblues.
Since blue is a complementary color to yellow and can appear to cancel it out, strong blue fluorescence had especially better color appearance with lower color graded diamonds that have a slight yellowish tint such as I or J color but had little effect on the more colorless D, E and F color grades.
A clean diamond is more brilliant and fiery than the same diamond when it is "dirty". Dirt or grease on the top of a diamond reduces its luster.
Even a thin film absorbs some light that could have been reflected to the viewer. Colored dye or smudges can affect the perceived color of a diamond.
Current practice is to clean a diamond thoroughly before grading its color. Maintaining a clean diamond can sometimes be difficult as jewelry settings can obstruct cleaning, and oils, grease, and other hydrophobic materials adhere well to a diamond.
Many jewelers use steam cleaners. Some jewelers provide their customers with ammonia -based cleaning kits; ultrasonic cleaners are also popular.
Historically, it has been claimed that diamonds possess several supernatural powers:. Because of their extraordinary physical properties , diamonds have been used symbolically since near the time of their first discovery.
Perhaps the earliest symbolic use of diamonds was as the eyes of Hindu devotional statues. Vajra is the word for diamond and ayudham means weapon in Sanskrit.
Another name for it was Agira which means fire or the sun. In fact there are 14 names counted to be given to a diamond in traditional Hinduism. The oldest dated printed book in the world is called the Diamond Sutra , a Chinese text dating from and was found in the Mogao Caves.
Sutras are most used to describe the teachings of Buddha. Jewel imagery forms a central part of Buddhism: The book presently resides in the British Library.
Many cultures use divine intervention to explain the origin and creation of gemstones, and diamonds were no exception to this.
In Greek mythology for example it was the youth on the island of Crete that disturbed Zeus and who were then as a form of punishment transformed into the adamas.
Philosophers however had a more naturalistic approach to explain the origin of gems: Plato for example believed gemstones were a consequence of fermentation in the stars, where a diamond actually formed the kernel of gold-bearing mass.
In later times, Robert Boyle actually believed that gems including a diamond were formed of clear, transparent water, and that their colors and characteristics were derived from their metallic spirit.
The diamond is the birthstone for people born in the month of April, and is also used as the symbol of a sixty-year anniversary , such as a Diamond Jubilee see hierarchy of precious substances.
In a system of heraldry by gemstone occasionally used in the past for the arms of nobles, diamond was used to represent the color sable, or black. The origin of the custom to use diamonds in rings, and more recently, in engagement rings , can be traced back to the Middle Ages and even the Romans.
The Romans valued the diamond entirely on account of the supernatural powers they ascribed to it. Pliny wrote that a diamond baffles poison, keeps off insanity, and dispels vain fears.
On this account it was recommended as the stone to be set in wedding or espousal rings—not on account of its beauty therefore, which was described by Isidore of Seville as a small stone devoid of beauty.
One of the first occurrences of the diamond engagement or wedding ring can be traced back to the marriage of Maximilian I then Archduke of Austria to Mary of Burgundy in The popularity of the diamond ring as an engagement ring for a much wider audience can be traced directly to the marketing campaigns of De Beers , starting in In the early 20th century, a chairman of De Beers optimistically predicted that the diamond trade would prosper "so long as men are foolish and women are vain.
Today, the round brilliant is still the most popular diamond shape for an engagement ring. More than 60 percent of diamonds on the market are brilliants.
The increase in online sales are disrupting the market for diamonds by bringing greater transparency to an industry that has traditionally relied on opacity.
In some of the more politically unstable central African and west African countries, revolutionary groups have taken control of diamond mines , using proceeds from diamond sales to finance their operations.
Diamonds sold through this process are known as conflict diamonds or blood diamonds. Major diamond trading corporations continue to fund and fuel these conflicts by doing business with armed groups.
In response to public concerns that their diamond purchases were contributing to war and human rights abuses in central Africa and West Africa , the United Nations , the diamond industry and diamond-trading nations introduced the Kimberley Process in , which is aimed at ensuring that conflict diamonds do not become intermixed with the diamonds not controlled by such rebel groups, by providing documentation and certification of diamond exports from producing countries to ensure that the proceeds of sale are not being used to fund criminal or revolutionary activities.
From Wikipedia, the free encyclopedia. Diamond mining in India. Big Hole and De Beers. A chief product of Naxos has long been a high grade of amorphous corundum which was used as an abrasive.
Richards, Ohio State University, , page They further discuss his referral to the adamas coming from the "east" through Armenian traders, but they show this was actually based on an erroneous interpretation of Theophrastus.
Williams, Diamond Mines of South Africa, New York, BF Buck Company, argues that the stone named " adamas " by the Greek and further referred to by Pliny was most likely a sapphire, since this was a much more abundant stone, even among traders in Asia, than diamond especially when used in the context of " adamas " being an ornamental stone and not used in an "industrial" context of engraving gems.
There seems to be a consensus over a large period of time that in fact the " adamas " was not a diamond, but mostly any type of corundum, several other minerals such as spinel were probably confused with diamonds as well; particularly because of a similarity in hardness and their availability in the Mediterranean area.
He describes diamonds being worn as long as years ago, recorded in ancient Hindu writings. Devotional statues is not specifically mentioned.
Diamonds, Gold, and War: Archived from the original on The Autobiography of John Hays Hammond. Antwerp World Diamond Center. How to Buy a Diamond: How to Buy Diamonds, Pearls, Colored The nature of diamonds.
Handbook of carbon, graphite, diamond, and fullerenes: Retrieved March 1, An Encyclopaedia of Occultism. Leipzig, Verlag von S.
Precious Stones in Nature, Art and Literature. An Essay about the Origin and Virtue of Gems. Fire in the Earth, the Story of the Diamond.
NY, Harper and Brothers. Diamonds can also form polycrystalline aggregates. There have been attempts to classify them into groups with names such as boart , ballas , stewartite and framesite, but there is no widely accepted set of criteria.
There are many theories for its origin, including formation in a star, but no consensus. Diamond is the hardest known natural material on both the Vickers scale and the Mohs scale.
Diamond hardness depends on its purity, crystalline perfection and orientation: The hardness of diamond contributes to its suitability as a gemstone.
Because it can only be scratched by other diamonds, it maintains its polish extremely well. Unlike many other gems, it is well-suited to daily wear because of its resistance to scratching—perhaps contributing to its popularity as the preferred gem in engagement or wedding rings , which are often worn every day.
These diamonds are generally small, perfect to semiperfect octahedra, and are used to polish other diamonds.
Their hardness is associated with the crystal growth form, which is single-stage crystal growth. Most other diamonds show more evidence of multiple growth stages, which produce inclusions, flaws, and defect planes in the crystal lattice, all of which affect their hardness.
It is possible to treat regular diamonds under a combination of high pressure and high temperature to produce diamonds that are harder than the diamonds used in hardness gauges.
The toughness of natural diamond has been measured as 7. As with any material, the macroscopic geometry of a diamond contributes to its resistance to breakage.
Diamond has a cleavage plane and is therefore more fragile in some orientations than others. Diamond cutters use this attribute to cleave some stones, prior to faceting.
Other specialized applications also exist or are being developed, including use as semiconductors: Boron substitutes for carbon atoms in the diamond lattice, donating a hole into the valence band.
Substantial conductivity is commonly observed in nominally undoped diamond grown by chemical vapor deposition. This conductivity is associated with hydrogen-related species adsorbed at the surface, and it can be removed by annealing or other surface treatments.
This property can be utilized to extract diamonds using oil when making synthetic diamonds. However, when diamond surfaces are chemically modified with certain ions, they are expected to become so hydrophilic that they can stabilize multiple layers of water ice at human body temperature.
The surface of diamonds is partially oxidized. The oxidized surface can be reduced by heat treatment under hydrogen flow.
That is to say, this heat treatment partially removes oxygen-containing functional groups. The structure gradually changes into sp 2 C above this temperature.
Thus, diamonds should be reduced under this temperature. Diamonds are not very reactive. Under room temperature diamonds do not react with any chemical reagents including strong acids and bases.
This means that pure diamond should transmit visible light and appear as a clear colorless crystal. Colors in diamond originate from lattice defects and impurities.
The diamond crystal lattice is exceptionally strong, and only atoms of nitrogen , boron and hydrogen can be introduced into diamond during the growth at significant concentrations up to atomic percents.
Transition metals nickel and cobalt , which are commonly used for growth of synthetic diamond by high-pressure high-temperature techniques, have been detected in diamond as individual atoms; the maximum concentration is 0.
Virtually any element can be introduced to diamond by ion implantation. Nitrogen is by far the most common impurity found in gem diamonds and is responsible for the yellow and brown color in diamonds.
Boron is responsible for the blue color. Plastic deformation is the cause of color in some brown  and perhaps pink and red diamonds. Colored diamonds contain impurities or structural defects that cause the coloration, while pure or nearly pure diamonds are transparent and colorless.
Most diamond impurities replace a carbon atom in the crystal lattice , known as a carbon flaw. The most common impurity, nitrogen, causes a slight to intense yellow coloration depending upon the type and concentration of nitrogen present.
Diamonds of a different color, such as blue, are called fancy colored diamonds and fall under a different grading scale. In , the Wittelsbach Diamond , a Diamonds can be identified by their high thermal conductivity.
Their high refractive index is also indicative, but other materials have similar refractivity. Diamonds cut glass, but this does not positively identify a diamond because other materials, such as quartz, also lie above glass on the Mohs scale and can also cut it.
Diamonds can scratch other diamonds, but this can result in damage to one or both stones. Hardness tests are infrequently used in practical gemology because of their potentially destructive nature.
Diamonds also possess an extremely high refractive index and fairly high dispersion. Taken together, these factors affect the overall appearance of a polished diamond and most diamantaires still rely upon skilled use of a loupe magnifying glass to identify diamonds "by eye".
Diamonds are extremely rare, with concentrations of at most parts per billion in source rock. Loose diamonds are also found along existing and ancient shorelines , where they tend to accumulate because of their size and density.
However, there are other sources. Some blocks of the crust, or terranes , have been buried deep enough as the crust thickened so they experienced ultra-high-pressure metamorphism.
These have evenly distributed microdiamonds that show no sign of transport by magma. In addition, when meteorites strike the ground, the shock wave can produce high enough temperatures and pressures for microdiamonds and nanodiamonds to form.
A common misconception is that diamonds are formed from highly compressed coal. Coal is formed from buried prehistoric plants, and most diamonds that have been dated are far older than the first land plants.
It is possible that diamonds can form from coal in subduction zones , but diamonds formed in this way are rare, and the carbon source is more likely carbonate rocks and organic carbon in sediments, rather than coal.
Diamonds are far from evenly distributed over the Earth. The Argyle diamond mine in Australia , the largest producer of diamonds by weight in the world, is located in a mobile belt , also known as an orogenic belt ,  a weaker zone surrounding the central craton that has undergone compressional tectonics.
Instead of kimberlite, the host rock is lamproite. Lamproites with diamonds that are not economically viable are also found in the United States, India and Australia.
Kimberlites can be found in narrow 1 to 4 metres dikes and sills, and in pipes with diameters that range from about 75 m to 1. Fresh rock is dark bluish green to greenish gray, but after exposure rapidly turns brown and crumbles.
They are a mixture of xenocrysts and xenoliths minerals and rocks carried up from the lower crust and mantle , pieces of surface rock, altered minerals such as serpentine , and new minerals that crystallized during the eruption.
The texture varies with depth. The composition forms a continuum with carbonatites , but the latter have too much oxygen for carbon to exist in a pure form.
Instead, it is locked up in the mineral calcite Ca C O 3. All three of the diamond-bearing rocks kimberlite, lamproite and lamprophyre lack certain minerals melilite and kalsilite that are incompatible with diamond formation.
In kimberlite, olivine is large and conspicuous, while lamproite has Ti- phlogopite and lamprophyre has biotite and amphibole. They are all derived from magma types that erupt rapidly from small amounts of melt, are rich in volatiles and magnesium oxide , and are less oxidizing than more common mantle melts such as basalt.
These characteristics allow the melts to carry diamonds to the surface before they dissolve. Kimberlite pipes can be difficult to find.
They weather quickly within a few years after exposure and tend to have lower topographic relief than surrounding rock. If they are visible in outcrops, the diamonds are never visible because they are so rare.
In any case, kimberlites are often covered with vegetation, sediments, soils or lakes. In modern searches, geophysical methods such as aeromagnetic surveys , electrical resistivity and gravimetry , help identify promising regions to explore.
This is aided by isotopic dating and modeling of the geological history. Then surveyors must go to the area and collect samples, looking for kimberlite fragments or indicator minerals.
The latter have compositions that reflect the conditions where diamonds form, such as extreme melt depletion or high pressures in eclogites.
However, indicator minerals can be misleading; a better approach is geothermobarometry , where the compositions of minerals are analyzed as if they were in equilibrium with mantle minerals.
Finding kimberlites requires persistence, and only a small fraction contain diamonds that are commercially viable. The only major discoveries since about have been in Canada.
Since existing mines have lifetimes of as little as 25 years, there could be a shortage of new diamonds in the future. Diamonds are dated by analyzing inclusions using the decay of radioactive isotopes.
Depending on the elemental abundances, one can look at the decay of rubidium to strontium , samarium to neodymium , uranium to lead , argon to argon , or rhenium to osmium.
Those found in kimberlites have ages ranging from 1 to 3. The kimberlites themselves are much younger. Most of them have ages between tens of millions and million years old, although there are some older exceptions Argyle, Premier and Wawa.
Thus, the kimberlites formed independently of the diamonds and served only to transport them to the surface. The reason for the lack of older kimberlites is unknown, but it suggests there was some change in mantle chemistry or tectonics.
No kimberlite has erupted in human history. Most gem-quality diamonds come from depths of — km in the lithosphere.
Such depths occur below cratons in mantle keels , the thickest part of the lithosphere. These regions have high enough pressure and temperature to allow diamonds to form and they are not convecting, so diamonds can be stored for billions of years until a kimberlite eruption samples them.
Host rocks in a mantle keel include harzburgite and lherzolite , two type of peridotite. The most dominant rock type in the upper mantle, peridotite is an igneous rock consisting mostly of the minerals olivine and pyroxene ; it is low in silica and high in magnesium.
However, diamonds in peridotite rarely survive the trip to the surface. A smaller fraction of diamonds about have been studied come from depths of — km, a region that includes the transition zone.
They formed in eclogite but are distinguished from diamonds of shallower origin by inclusions of majorite a form of garnet with excess silicon.
A similar proportion of diamonds comes from the lower mantle at depths between and km. Diamond is thermodynamically stable at high pressures and temperatures, with the phase transition from graphite occurring at greater temperatures as the pressure increases.
Thus, underneath continents it becomes stable at temperatures of degrees Celsius and pressures of 4. In subduction zones, which are colder, it becomes stable at temperatures of degrees C and pressures of 3.
At depths greater than km, iron-nickel metal phases are present and carbon is likely to be either dissolved in them or in the form of carbides.
Thus, the deeper origin of some diamonds may reflect unusual growth environments. In the first known natural samples of a phase of ice called Ice VII were found as inclusions in diamond samples.
The inclusions formed at depths between and km, straddling the upper and lower mantle, and provide evidence for water-rich fluid at these depths.
The amount of carbon in the mantle is not well constrained, but its concentration is estimated at 0. This ratio has a wide range in meteorites, which implies that it was probably also broad in the early Earth.
It can also be altered by surface processes like photosynthesis. This variability implies that they are not formed from carbon that is primordial having resided in the mantle since the Earth formed.
Instead, they are the result of tectonic processes, although given the ages of diamonds not necessarily the same tectonic processes that act in the present.
Diamonds in the mantle form through a metasomatic process where a C-O-H-N-S fluid or melt dissolves minerals in a rock and replaces them with new minerals.
Diamonds form from this fluid either by reduction of oxidized carbon e. Using probes such as polarized light, photoluminescence and cathodoluminescence , a series of growth zones can be identified in diamonds.
The characteristic pattern in diamonds from the lithosphere involves a nearly concentric series of zones with very thin oscillations in luminescence and alternating episodes where the carbon is resorbed by the fluid and then grown again.
Diamonds from below the lithosphere have a more irregular, almost polycrystalline texture, reflecting the higher temperatures and pressures as well as the transport of the diamonds by convection.
Geological evidence supports a model in which kimberlite magma rose at 4—20 meters per second, creating an upward path by hydraulic fracturing of the rock.
As the pressure decreases, a vapor phase exsolves from the magma, and this helps to keep the magma fluid.
Then, at lower pressures, the rock is eroded, forming a pipe and producing fragmented rock breccia. As the eruption wanes, there is pyroclastic phase and then metamorphism and hydration produces serpentinites.
Although diamonds on Earth are rare, they are very common in space. In meteorites , about three percent of the carbon is in the form of nanodiamonds , having diameters of a few nanometers.
Sufficiently small diamonds can form in the cold of space because their lower surface energy makes them more stable than graphite.
The isotopic signatures of some nanodiamonds indicate they were formed outside the Solar System in stars. High pressure experiments predict that large quantities of diamonds condense from methane into a "diamond rain" on the ice giant planets Uranus and Neptune.
Diamonds may exist in carbon-rich stars, particularly white dwarfs. One theory for the origin of carbonado , the toughest form of diamond, is that it originated in a white dwarf or supernova.
The most familiar uses of diamonds today are as gemstones used for adornment , and as industrial abrasives for cutting hard materials.
The markets for gem-grade and industrial-grade diamonds value diamonds differently. The dispersion of white light into spectral colors is the primary gemological characteristic of gem diamonds.
In the 20th century, experts in gemology developed methods of grading diamonds and other gemstones based on the characteristics most important to their value as a gem.
Four characteristics, known informally as the four Cs , are now commonly used as the basic descriptors of diamonds: A large, flawless diamond is known as a paragon.
A large trade in gem-grade diamonds exists. Although most gem-grade diamonds are sold newly polished, there is a well-established market for resale of polished diamonds e.
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