The diamond is a Minéral composed of Carbone, of which it represents the allotrope high pressure, which crystallizes in the crystalline Système cubic. It is hardest (Dureté Mohs of 10) of all natural materials.
EtymologyThe word is derived from the Greek αδαμας ( adamas : “untameable”, of adamastos : “inflexible, inébranlable”, which also gave Adamantin and adamant, old name of the diamond), which indicated the hardest metal initially, then any very hard matter, like the Magnétite. It was thus used to indicate a large variety of Gemme S, such as (all these denominations are from now on prohibited, except indication of the source of a genuine diamond) :
- the Corundum synthétique : diamond of alumina ;
- the Hematite : black diamond of Nevada , diamond of Alaska (black hematite) ;
- the Obsidian décolorée : diamond of Nevada ;
- the Pyrite : alpine diamond , diamond of Pennsylvania ;
- the quartz :
- diamond of Bohemia , of Briançon , of Brighton , Bristol-board , of Buxton , of Hawaii ; Irish diamond , Mexican diamond , Western diamond ;
- diamond Marmorosch (variety of quartz) ;
- diamond of Alaska , diamond of Brazil (rock crystal) ;
- diamond of Alençon , German diamond (smoked out quartz) ;
- diamond of Arkansas (quartz also named Horatio Diamond) ;
- diamond of Colorado (transparent smoked quartz) ;
- diamond of Dauphine the , diamond of Rennes (hyaline quartz) ;
- the Zircon : diamond of Ceylon (colorless), diamond of Matura (faded zircon).
HistoryThe discovery in 1793 of its composition, of the pure Carbon, by Antoine Lavoisier, marked the beginning of the epopee of its synthesis. However, it was necessary to await the middle of the 20th century so that finally chemists succeed in manufacturing it. Consequently, diamond became an industrial material whose annual production reaches today more 400 million Carat S, is 80 tons.
PropertiesDiamond is a metastable form Carbone under the conditions of temperature and pressure normals. It burns as of 500°C in a draft, but if it is maintained with: 1100°C under neutral atmosphere, it is transformed into graphite.
In its natural state, diamond has a structure Cubique with centered faces (where a tetrahedral site on two is occupied) and eight Atome S by elementary mesh.
This structure is noted A4 in notation '' Strukturbericht ''. Its Groupe of space is (n°227), its Symbole of Pearson is cF8. Its cell parameter is:
- has = 3,566 7 Å
Physical propertiesIts molar Masse is of 12,02 G·mol-1, its Density measured is of: 3520 kg/m 3 .
In the crystalline building of diamond, the connections between carbon atoms result from the pooling of the electrons of the peripheral layer in order to form saturated layers. Each carbon atom is thus associated in a tetrahedral way with its four closest neighbors (hybridization sp3 of carbon), and thus supplements its external layer. These connections Covalent S, strong and thus difficult to break, cover all the crystal, from where its incredible hardness.
The electric Conductivité is low, because the electrons do not gather as in a métal : they remain related to the atoms and cannot, for example under the action of an external electric field, to form an electronic cloud which would transport the current continuously. In other words, diamond is a very good insulator. Nevertheless, it is the subject of studies as a Semi-conducteur with broad band for the electronic of power.
The thermal Conductivité of diamond is exceptional, which explains why it appears so cold with the touch. This mineral is, by far, the best known driver of heat. In an electrical crystal insulator like diamond, thermal conductivity is ensured by the coherent vibrations of the atoms of the network. Values of: 2500 W (m·K) were measured, that one can compare with the 401 W (m·K) of copper and with the 429 W (m·K) of the money. This property makes of it a candidate like substrate for the cooling of the Semi-conducteur S.
Lastly, the coefficient of Dilation of diamond, related to the properties of the vibrations of the network of this material, is very low. For pure diamond, the relative increase length per degree is of approximately one millionth with room temperature, which one can compare with the 1,2 millionth Invar, alloy made up of 64 % of iron and 36 % of nickel, which is famous for its very weak dilation. Iron is very far behind, with 11,7 millionth.
Optical propertiesDiamond is transparent or translucide ; its index of refraction is particularly high, and varies according to the length of onde : these are the properties which give him its characteristic glare, “ adamantin ”. This index is of 2,407 for the light Rouge (687 Nm), 2,418 for the Yellow light , and 2,451 for the light Blue E (431 Nm).
FormationDiamonds consist of Carbone. They are formed when this last is under conditions of very high temperature and pressure, between 1100 °C and 1400 °C, which corresponds to depths of approximately 180 km in the terrestrial coat. Impurities such as the Nitrogen, the Sulfur or of metals can color diamond. Natural diamonds are composed of carbon which was in the coat since the formation of the Ground, but some consist of carbon coming from organizations, such as Algue S. It is what reveals the isotopic composition carbon. This organic carbon was hidden to the terrestrial coat by the movement of the tectonic plates, in the zones of Subduction.
Increase on the surfaceDiamonds of South Africa were re-installed by very powerful eruptions Volcan ic. They caused the formation of brêches volcanic, consisted of remains of very deep rocks in the beginning. Diamonds are thus found in inclusion in these rocks called Kimberlite S. The erosion can then transport them and incorporate them in alluvial sediments .
LayersThe majority of diamonds are extracted from the Kimberlite presents in the oldest zones of continental Croûte (at least 1,5 billion years). See Craton.
Until the 16th century, the India and more particularly the area of Golkonda (Golconde) were the only diamond production zone in the world, with the area of Borneo. It is in India that were extracted more famous old diamonds. Then the layers of Brazil were discovered. They fed the Western market until the end of the 19th century, date of discovered South-African layers.
Since this date, the majority of diamonds come from Africa (62,1 % in 1999). This situation was the origin of several wars like that of the Sierra Leone, where the strategic objectives were the control of the principal layers of the country to finance the conflict.
Producer countriesIn 2005, the worldwide production of diamonds was of 173,5 million Carat S and the four principal producers are the Russia, the Botswana, the Australia and the Democratic republic of Congo which produce with them four a little more than 73% of the worldwide production.
The process of extraction is very diversified, since it depends on the area in which diamond is exploited. But, in general, the operations are divided into three parties :
- the elimination of the sterile elements (ground and stone which covers diamantiferous sand);
- the extraction;
Because of the cost of the exploitation of the mines (ten tons of ore make it possible to extract only a Carat from diamond), only the companies invest in these zones which guarantee an important production to them: generally, of the square kilometers of ground are excavated to obtain an appreciable gem of size, from where the cost of diamonds.
Diamonds of synthesis
See also: synthetic Diamond
Since it is known that diamond is only the one particular shape of carbon, the physicists and chemists tried to synthesize it. The first artificial synthesis of diamond took place in 1953 with Stockholm by the inventor Baltzar von Platen and the young civil engineer Anders Kämpe working in Swedish company ASEA.
By subjecting carbon to a strong pressure and a high temperature during several hours, it is possible to carry out a diamond of synthesis. But because of their small size, the latter are used only in industry.
UseIn addition to the Jewelry, diamond is used in industry because of its properties, in particular of hardness.
IndustryFirst of all, industry uses much diamond because of its hardness. Since the machining and cutting tools based on the mechanical properties of diamond, until the anvils with diamond making it possible to recreate titanic pressures, the applications are multiple. This hardness also intervenes in the precision which one can reach with diamond tools. In particular, the Scalpel S out of diamond, make it possible to create incisions ultraprécises (in Ophtalmologie for example), because the least touch cuts out the skin. In addition, the diamond making up of carbon, it is biocompatible and does not generate a rejection or of toxicity.
The Chimie is also strongly interested in the diamant : it has properties which make it completely suitable for applications in electrochemistry. On the one hand, it is resistant to the Acide S and the bases, which allows a use in corrosive mediums. In addition, the diamond electrodes plunged in pure water do not undergo any reaction électrochimique ; they are thus very effective.
Many optical devices use the transparency of diamond, while the electronic devices exploit in particular its thermal properties.
Because of its low electric conductivity, diamond can be used in the industry of the Semi-conducteur S when he is doped with impurities of Bore or of Phosphore.
Diamonds are currently being studied for a use as détecteurs :
- of Radiation S in installations of scientific research. CERN was to receive several square meters of synthetic diamond detectors. Technology not having advanced rather quickly, they will be in Silicium;
- of radiations in the installations of Radiotherapy. The carbon of diamond is the same one as that of the body (normal carbon 12) and thus allows measurements of amount closer to the amount really received by fabrics;
- of various products, by the methods of the type SAW ( Surface Acoustic Waves ), because diamond is a very good Transducteur, thanks to its rigidity. It is however necessary to deposit (by methods of CVD-Magnetron, in particular) a thin film of Nitrure of aluminum, which is a piezoelectric , contrary to diamond. The form of the deposit influences the detectable products.
The production of natural diamond is mainly intended for industry.
JewelryQualities of certain diamonds (like their purity, their important size and their color) make the diamond, most famous of the invaluable stones in jewelry.
The beauty of its brilliance is due to the fact that it has a top Index of refraction of the light and a great capacity dispersif : while penetrating, the rays of light are considered inside the stone ad infinitum and the white light disperses, turns over inside transformed into a range of colors. Diamonds (as the water drops) function like prisms while slowing down, more or less according to the wavelengths (Violet you to the maximum, red at least) so that the colors are dispersed in the form of Arc-en-ciel.
But all diamonds are not used in jewelry. Any defect can remove value to them and they are then employed for industrial applications. Generally this arrives with those which present internal bubbles or foreign particles, or if they of irregular form or are poorly coloured.
CutThe size of diamonds is carried out especially in Antwerp (Belgium), in Tel-Aviv (Israel) and Gujarat (India) by the community jaïn. In Thailand, in fact the invaluable stones (ruby and sapphires) are cut.
The degree of the beauty of the rainbow of diamond depends, mainly, of the sculpture and of polished stone. Although naturally diamonds have their own glares, those can be improved and multiplied by the expert size of concise.
Because of its extreme hardness, diamond can be machined only by another diamond, this is why the sculpture and the polish of the stone are the most important elements.
Before cutting it, one examines the gem to determine his plans of cleavage. One then traces on it a line which marks the perimeter of these plans. On this one, one makes a small groove with a wood species which carries in its end a diamond. By this opening, one introduces a steel expert swordsman, one gives a dry blow and the stone is divided into two.
There exists in many ways to cut the diamond, but the most known, that which best emphasizes the beauty of the diamond and which of this fact is used, is certainly the size “ brillant ”. This sophisticated technique makes it possible to transform the rough stones into true jewels of light, by revealing 58 facets (57 if one does not take account of the Colette): 33 on the crown and 24 on the cylinder head, regular and of precisely defined sizes, on the surface of diamond.
Indeed, if the concepts of purity and color appear familiar, the proportions of size are it more rarely. However, these last are an essential factor of quality. They directly condition returned brightness and the “ feu ” of diamond. With identical color, a having diamond of good proportions will be much brighter than an incorrectly cut pure diamond.
Since the appearance of the size Tolkovskyen (1919), the diamond cutters did not cease seeking to optimize returned brightness of diamond. Of all the sizes of diamond, it is certainly the round form brilliance which was studied and which is succeeded; today, the proportions applied to this size result directly from the comprehension of the optical laws of material and the control of the technique of size and polishing.
In Japan the size arrow and hearts is very appreciated, named thus because of the forms of the plays of light.
The apprentices tailors are very rare today, the size being realized more and more by of the lasers using information processing systems|date= September 25th, 2007
ColorDiamonds are also classified by color. The most common color being “the white” (here, the white indicates the absence of color rather: i.e. diamond is transparent). These colors are noted thanks to a code using the various letters of the alphabet:
PurityDiamonds contain also a large variety of inclusions which can modify its appearance. An inclusion, or impurity, is called a “ clamping plate ”. Those are indicated by using the following codes:
Diamond cutters and gemmologistsIt classification of categories of diamond (4C) is realized by professionals. One calls the people in charge of this work the gemmologists. There exists little of world laboratories of gemmology, most known are:
- Gemological Institute off America (GIA) with New York
- Diamond High Council (HRD) with Antwerp
- International Gemological Institute (IGI) in Antwerp
- American Gem Society (AGS) in New York
The diamond cutter a contrario of the gemmologist does not study the invaluable stone but negotiates it and carries out if necessary a mounting to emphasize it. He works only of the cut stones but not of rough stones.
Famous diamondsList few diamonds célèbres :
Recent discoveryThe largest diamond of the world was discovered on August 25th, 2007 in a South-African mine and would weigh the double of the Cullinan which weighs 3106 carats. Diamond was transported to Johannesbourg.
The largest diamond ever sold with the biddingsNovember 15th, 2007, a diamond of 84,37 carats allocated 16,2 million dollars (11 million euros) to the founder of the chain of Guess clothing? , Georges Marciano, at the time of an auction at the house Sotheby' S in Geneva. It is about the largest diamond ever sold with the biddings. Its price had been evaluated between 13,3 million and 17,8 million dollars (9,05 to 12,1 million euros). Diamond thus takes down the second place with the classification of the invaluable stones and jewels having gained the largest sums with the biddings. In May 1995, a diamond of 100,1 carats had been allocated 16,5 million dollars at the time of a sale to the same branch of Sotheby' S to Geneva.
- the Noces of diamond symbolize the 60 years of Marriage in the Folklore French.
- diamond is the 13th level in the progression of the Sarbacane Sportive.
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