Diamonds of a different color
U.K. bookings were also hit by better-than-expected summer weather and quiet trading during the world Cup. Meanwhile, the Icelandic volcanic-ash cloud forced customers to question if they would be able to take already-booked holidays and if they would be able to return home, said Paul Bowtell, TUI’s finance chief.
Somewhat related to hardness is another mechanical property toughness, which is a material’s ability to resist breakage from forceful impact. The toughness of natural diamond has been measured as 2.0 MPa·m1/2,[17] and the CHEAP SHOES critical stress intensity factor is 3.4 MN·m−3/2.[18] Those values are good compared to other gemstones, but poor compared to most engineering materials. 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.[19]
Electrical conductivity
Other specialized applications also exist or are being developed, including use as semiconductors: some blue diamonds are natural semiconductors, in contrast to most diamonds, which are excellent electrical insulators.[20] The conductivity and blue color originate from boron impurity. Boron substitutes for carbon atoms in the diamond lattice, donating a hole into the valence band.[20]
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.[21][22]
Color
Main article: Diamond color
A museum display of jewelry items. Three brooches each consist of a large brown central gem surrounded by many clear small stones. A necklace has a large brown gem at its bottom and its string is all covered with small clear gems. A cluster-shaped decoration contains many brown gems.
Brown diamonds at the National Museum of Natural History in Washington, D.C
Diamond has a wide bandgap of 5.5 eV corresponding to the deep ultraviolet wavelength of 225 nanometers. This means 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 Ni and Co, 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 0.01% for Ni[23] and even much less for Co. Virtually any element can be introduced to diamond by ion implantation.[24]
Other specialized applications also exist or are being developed, including use as semiconductors: some blue diamonds are natural semiconductors, in contrast to most diamonds, which are excellent electrical insulators.[20] The conductivity and blue color originate from boron impurity. Boron substitutes for carbon atoms in the diamond lattice, donating a hole into the valence band.[20]
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.[21][22]
Color
Main article: Diamond color
A museum display of jewelry items. Three brooches each consist of a large brown central gem surrounded by many clear small stones. A necklace has a large brown gem at its bottom and its string is all covered with small clear gems. A cluster-shaped decoration contains many brown gems.
Nitrogen is by far the most common impurity found in gem diamonds. Nitrogen is responsible for the yellow and brown color in diamonds. Boron is responsible for the gray blue colors.[11] Color in diamond has two additional sources: irradiation (usually by alpha particles), that causes the color in green diamonds; and plastic deformation of the diamond crystal lattice. Plastic deformation is the cause of color in some brown[25] and perhaps pink and red diamonds.[26] In order of rarity, colorless diamond, by far the most common, is followed by yellow and brown, by far the most common colors, then by blue, green, black, translucent white, pink, violet, orange, purple, and the rarest, red.[19] “Black”, or Carbonado, diamonds are not truly black, but rather contain numerous dark inclusions that give the gems their dark appearance. 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.[19] The Gemological Institute of America (GIA) classifies low saturation yellow and brown diamonds as diamonds in the normal color range, and applies a grading scale from “D” (colorless) to “Z” (light yellow). Diamonds of a different color, such as blue, are called fancy colored diamonds, and fall under a different grading scale.[19]
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