sábado, 19 de janeiro de 2013


Some diamonds scattered demonstrate its various facets reflected.
CategoryNative Minerals
Chemical FormulaC
Molecular weightUl = 12.01 g / mol
ColorTypically yellow, brown or gray to colorless. Less often blue, green, black, translucent white, pink, violet, orange, purple and red.
Crystal habitOctahedron
Crystal systemCubic )
Cleavage111 (perfect in four directions)
Hardness  Mohs10
Refractive index2418 (500 nm)
Ultraviolet FluorescenceColorless
Specific gravity3:52 + / - 0.01
Density3.5- g / cm 3 
Melting pointDependent pressure
TransparencyTransparent  to translucent to subtransparente
The  diamond  shape is an  allotrope of  carbon , in  the chemical formula  C .It is the thermodynamically stable form of carbon at pressures above 60 kbar.Marketed as precious gems, diamonds have a high added value. Typically, the diamond cubic structure crystallizes and can be synthesized industrially. Another form of diamond crystallization is hexagonal, also known as  lonsdaleitaless common in nature and lesser hardness (7-8 on  the Mohs scale ). The characteristic that differs from the diamond allotropic forms, is that each carbon atom in being sp ³ hybridized, and finding is connected to 4 other carbon atoms by covalent bonds in a three-dimensional tetrahedral arrangement. The diamond can be converted to graphite, the thermodynamically stable allotrope at low pressures, applying temperatures above 1500 ° C under vacuum or inert atmosphere. Under ambient conditions, this conversion is extremely slow, making it neglected.
Crystallizes  in the  cubic system , generally in  crystals  to form  octahedral (eight-sided) or hexaquisoctaédrica (48 faces), often with curved surfaces, rounded, colorless or colored. The dark-colored diamonds are little known and its value as a gemstone is lower due to its unattractive appearance. Unlike what was thought for years, diamonds are not forever because the  carbon  decays with time, but diamonds last longer than any human being .
Being  carbon  pure diamond glows when exposed to a flame, turning into  carbon dioxide . It is soluble in many  acids  and infusible except at high pressures.
Diamond is the hardest material known naturally occurring, with a hardness of 10 (maximum  Mohs scale ). This means it can not be scratched by any mineral or other substance except the diamond itself, functioning as an important abrasive material. However, it is very fragile, this fact is due to the perfect octahedral cleavage on {111}. These two features have made ​​the diamond was not tailored for many years. The largest deposits in the world are from Africa Sul.Outras important deposits are located in Russia (second largest producer) and Australia (third largest producer), among others of lesser importance. [1]
The  density  is 3.48. The adamantine luster is derived from the very high index of  refraction (2.42). It will be recalled that all mineral content of  refraction greater than or equal to 1.9 hold this brightness. However, the uncut crystals may exhibit a greasy shine. You can display  fluorescence under light ultraviolet , causing stains blue, pink, yellow or green.


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edit ]Electrical Conductivity

Some blue diamonds are natural semiconductors, in contrast to most diamonds, which are excellent electrical insulators. [2]  Substantial conductivity is commonly observed in undoped diamond grown by  chemical vapor deposition and can be removed using certain treatments to the surface. [3] [4]

edit ]Other

Diamonds are lipophilic and hydrophobic, which means that the surface of a diamond can not be wetted by water but can easily be wet and damaged by oil. [5]
Under room temperature diamonds do not react with most chemicals, includindo various types of acids and alkalis. Thus, acids and alkalis can be used to refine synthetic diamonds. [5]


A face of a rough diamond.
Use as adornment (gem) is ancient in India was used to identify the varieties.
By having large refractive index, is the brightest gem.Because it is the hardest substance in nature, "not tall" and therefore its brilliance is eternal.
Diamonds that have no jeweler will use industrial use, because they are great abrasive.

The value of the gem diamond (using jeweler), like all things, depends on supply and demand. Since the diamond is a mineral abundant in nature, in the 1950s, the American Gemological Institute (GIA - Gemological Institute of America) created a classification standard to enable the commercialization of diamond globally. This pattern was created to classify diamonds range from colorless to tinted (slightly yellowish or greyish), naturally colored diamonds are rarer and have different classification.
The classification for the GIA scale from colorless to tinted is based on 4 variables, they are: WEIGHT, COLOR, PURITY and LAPPING. In English these variables are called Carat, Color, Clarity and Cut, thus forming the 4 C's of Diamond. These are items that make a diamond more valuable than another.


Weight: The unit of measurement for weighing gemstones is the carat (ct) in English Carat, 1 carat equals 0.2 grams. The price of a diamond 2CT is much greater than that of two diamonds 1ct as a diamond 2CT is much rarer. In this variable, the heavier the better.
Color: The color classification takes into account the tone of each diamond gems compared to the tone of matrices which are reference guides created by the GIA. This variable, as "more colorless" better. D - E - F - G - H - I - J - K - L - M - N - O - P ... Z
Purity: The purity of classification measures the amount, size and color of inclusions internal and surface characteristics. It was agreed that these characteristics included surface and has to be seen in a 10x loupe magnification. In this variable, the less the better. F - IF - VVS1 - VVS2 - VS1 - VS2 - SI1 - SI2 - I1 - I2 - I3
Cut: It is the action of man to take the raw yolk mehor these 3 variables before without compromising brightness, "fire" and the life of the diamond. The brilliant cut is the most popular diamond cut, about to be confused with the name of the mineral diamond. The brilliant cut, also known as stoning complete, is designed so that all the light that enters the yolk is reflected upward causing the diamond to shine even more. In this variable, the more brilliance, more fire, more better life. Without forgetting that the format of the gem also impacted by demand in its price, a round brilliant diamond can be more desired than a diamond triangular.


Once selected, the diamonds are cut and carve along the directions in which the hardness is smaller. A pulley as well conducted is one which enhances the focus, ie the set of colors derived from reflections of reflections.


Currently, there is a possibility of making synthetic diamond by subjecting  graphite  at elevated pressures. However, the results are nearly always crystals of reduced dimensions in order to be marketed as gemstones. The chance to purchase a  synthetic diamond  instead of a natural is almost nil, and even less chance of finding the gems that traders say are diamond but are not really.
The thermal stability of the synthetic diamond is less than the natural, for oxidative environment such as outdoors, the synthetic diamond oxidizes (grafitiza) at temperatures around 850 ° C.Already in a controlled atmosphere resistance graphitization is close to 1200 ° C.
Although already in  1880  J. Balentine Hannay, a  chemist  Scot , had produced tiny crystals, only in  1955  scientists at General Electric Company achieved an effective method for the synthesis of diamonds. This feat was credited to Francis Bundy, Tracy Hall, Herbert M. Strong and Robert H. Wentorf after investigations conducted by Percy W. Bridgeman at Harvard University.The diamonds thus obtained were industrial grade (not gemological), being nowadays produced on a large scale. Crystals with the quality of  gems , only able to synthesize in  1970  by  Strong and  Wentorf , a process that requires extremely high temperatures and pressures.

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