The high thermal conductivity of diamond makes it suitable as a heat sink for integrated circuits in electronics.
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The mining and distribution of natural diamonds are subjects of frequent controversy such as concerns over the sale of blood diamonds or conflict diamonds by African paramilitary groups. Only a very small fraction of the diamond ore consists of actual diamonds. The ore is crushed, during which care is required not to destroy larger diamonds, and then sorted by density. Today, diamonds are located in the diamond-rich density fraction with the help of X-ray fluorescence , after which the final sorting steps are done by hand.
Before the use of X-rays became commonplace,  the separation was done with grease belts; diamonds have a stronger tendency to stick to grease than the other minerals in the ore. Historically, diamonds were found only in alluvial deposits in Guntur and Krishna district of the Krishna River delta in Southern India. Diamond extraction from primary deposits kimberlites and lamproites started in the s after the discovery of the Diamond Fields in South Africa.
Most of these mines are located in Canada, Zimbabwe, Angola, and one in Russia. The Crater of Diamonds State Park in Arkansas is open to the public, and is the only mine in the world where members of the public can dig for diamonds. Australia boasts the richest diamantiferous pipe, with production from the Argyle diamond mine reaching peak levels of 42 metric tons per year in the s. In some of the more politically unstable central African and west African countries, revolutionary groups have taken control of diamond mines , using proceeds from diamond sales to finance their operations.
Diamonds sold through this process are known as conflict diamonds or blood diamonds.
In response to public concerns that their diamond purchases were contributing to war and human rights abuses in central and western Africa, the United Nations , the diamond industry and diamond-trading nations introduced the Kimberley Process in This is done by requiring diamond-producing countries to provide proof that the money they make from selling the diamonds is not used to fund criminal or revolutionary activities. Although the Kimberley Process has been moderately successful in limiting the number of conflict diamonds entering the market, some still find their way in.
This is a stringent tracking system of diamonds and helps protect the "conflict free" label of Canadian diamonds. Synthetic diamonds are diamonds manufactured in a laboratory, as opposed to diamonds mined from the Earth. The gemological and industrial uses of diamond have created a large demand for rough stones. This demand has been satisfied in large part by synthetic diamonds, which have been manufactured by various processes for more than half a century. However, in recent years it has become possible to produce gem-quality synthetic diamonds of significant size.
The majority of commercially available synthetic diamonds are yellow and are produced by so-called high-pressure high-temperature HPHT processes.
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Other colors may also be reproduced such as blue, green or pink, which are a result of the addition of boron or from irradiation after synthesis. Another popular method of growing synthetic diamond is chemical vapor deposition CVD. The growth occurs under low pressure below atmospheric pressure. It involves feeding a mixture of gases typically 1 to 99 methane to hydrogen into a chamber and splitting them to chemically active radicals in a plasma ignited by microwaves , hot filament , arc discharge , welding torch or laser.
A diamond simulant is a non-diamond material that is used to simulate the appearance of a diamond, and may be referred to as diamante. Cubic zirconia is the most common. The gemstone moissanite silicon carbide can be treated as a diamond simulant, though more costly to produce than cubic zirconia. Both are produced synthetically. Diamond enhancements are specific treatments performed on natural or synthetic diamonds usually those already cut and polished into a gem , which are designed to better the gemological characteristics of the stone in one or more ways.
These include laser drilling to remove inclusions, application of sealants to fill cracks, treatments to improve a white diamond's color grade, and treatments to give fancy color to a white diamond. Coatings are increasingly used to give a diamond simulant such as cubic zirconia a more "diamond-like" appearance. One such substance is diamond-like carbon —an amorphous carbonaceous material that has some physical properties similar to those of the diamond.
Advertising suggests that such a coating would transfer some of these diamond-like properties to the coated stone, hence enhancing the diamond simulant. Techniques such as Raman spectroscopy should easily identify such a treatment. Early diamond identification tests included a scratch test relying on the superior hardness of diamond.
This test is destructive, as a diamond can scratch another diamond, and is rarely used nowadays. Instead, diamond identification relies on its superior thermal conductivity. Electronic thermal probes are widely used in the gemological centers to separate diamonds from their imitations. These probes consist of a pair of battery-powered thermistors mounted in a fine copper tip.
One thermistor functions as a heating device while the other measures the temperature of the copper tip: This test takes about 2—3 seconds. Whereas the thermal probe can separate diamonds from most of their simulants, distinguishing between various types of diamond, for example synthetic or natural, irradiated or non-irradiated, etc. Those techniques are also used for some diamonds simulants, such as silicon carbide, which pass the thermal conductivity test.
Optical techniques can distinguish between natural diamonds and synthetic diamonds. They can also identify the vast majority of treated natural diamonds. Laboratories use techniques such as spectroscopy, microscopy and luminescence under shortwave ultraviolet light to determine a diamond's origin.
Several methods for identifying synthetic diamonds can be performed, depending on the method of production and the color of the diamond. CVD diamonds can usually be identified by an orange fluorescence.
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Screening devices based on diamond type detection can be used to make a distinction between diamonds that are certainly natural and diamonds that are potentially synthetic. Those potentially synthetic diamonds require more investigation in a specialized lab. Occasionally large thefts of diamonds take place. The gang broke through a perimeter fence and raided the cargo hold of a Swiss-bound plane. The gang have since been arrested and large amounts of cash and diamonds recovered. The identification of stolen diamonds presents a set of difficult problems. Rough diamonds will have a distinctive shape depending on whether their source is a mine or from an alluvial environment such as a beach or river—alluvial diamonds have smoother surfaces than those that have been mined.
Determining the provenance of cut and polished stones is much more complex. The Kimberley Process was developed to monitor the trade in rough diamonds and prevent their being used to fund violence. Before exporting, rough diamonds are certificated by the government of the country of origin. Some countries, such as Venezuela, are not party to the agreement. The Kimberley Process does not apply to local sales of rough diamonds within a country. Diamonds may be etched by laser with marks invisible to the naked eye.
Lazare Kaplan , a US-based company, developed this method. However, whatever is marked on a diamond can readily be removed. From Wikipedia, the free encyclopedia. This article is about the mineral. For the gemstone, see Diamond gemstone. The slightly misshapen octahedral shape of this rough diamond crystal in matrix is typical of the mineral.
Its lustrous faces also indicate that this crystal is from a primary deposit. Material properties of diamond and Crystallographic defects in diamond. A round brilliant cut diamond set in a ring. Diamond cutting and Diamond cut. List of diamond mines and Exploration diamond drilling. Kimberley Process , Blood diamond , and Child labour in the diamond industry. Gemology and Jewelry portal. Retrieved July 7, The Book of Diamonds.
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Colourless or pale blue stones are most valued, but these are rare; most gem diamonds are tinged with yellow. Most industrial diamonds are gray or brown and are translucent or opaque, but better-quality industrial stones grade imperceptibly into poor quality gems. The colour of diamonds may be changed by exposure to intense radiation as released in a nuclear reactor or by a particle accelerator or by heat treatment.
A very high refractive power gives the diamond its extraordinary brilliance.
A properly cut diamond will return a greater amount of light to the eye of the observer than will a gem of lesser refractive power and will thus appear more brilliant. The high dispersion gives diamonds their fire, which is caused by the separation of white light into the colours of the spectrum as it passes through the stone. The scratch hardness of diamond is assigned the value of 10 on the Mohs scale of hardness ; corundum, the mineral next to diamond in hardness, is rated as 9. The hardness of a diamond varies significantly in different directions, causing cutting and polishing of some faces to be easier than others.
For detailed physical properties, see native element table. In the atomic structure of diamond, as determined by X-ray diffraction techniques, each carbon atom is linked to four equidistant neighbours throughout the crystal. We welcome suggested improvements to any of our articles.
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