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Diamond Information
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DIAMOND

 
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Diamond is one of the natural allotropes of carbon (the main allotrope being graphite; see also allotropes of carbon). The hardest of naturally occurring materials, diamonds cut into multi-faceted shapes are among the most prized gemstones of jewelry, and find use in industrial applications as well.
 
Contents
 
1 Properties

1.1 Hardness and crystal structure
1.2 Toughness
1.3 Optical properties
1.4 Electrical properties
1.5 Thermal properties
1.6 Composition and color

2 The diamond industry

2.1 Cut

2.1.1 Cut Grading

2.2 Clarity
2.3 Color
2.4 Sources

3 Symbolism of diamonds

4 Related terms

5 Famous diamond cutters

6 Famous stones

7 See Also

8 External links

8.1 Labs, Cut, and General Links
8.2 Chemistry and Artificial Diamonds
8.3 Natural Sources and Marketing

9 Further reading

Diamond
A scattering of "brilliant" cut diamonds shows off the many reflecting facets.
A scattering of "brilliant" cut diamonds shows off the many reflecting facets.
General
Category Native Nonmetal, Mineral
Chemical formula Carbon, C
Identification
Color Most often colorless to white. Rarely pink, yellow, orange, green or blue.
Crystal habit Octahedral, spherical or massive
Crystal system Isometric
Cleavage Octahedral
Fracture Conchoidal
Mohs Scale hardness 10
Luster Adamantine to greasy
Refractive index index 2.417
Pleochroism None
Streak None
Specific gravity 3.516 - 3.525
Fusibility ?
Solubility ?
Major varieties
None
 
 
Properties
 
Diamond is a transparent, optically isotropic crystal with a refractive index of 2.417, a high dispersion of 0.044, and a specific gravity of 3.52.
 
Hardness and crystal structure
 
The diamond crystal bond structure gives the gem its hardness and differentiates it from graphite.
Sometimes known as adamant, it is the hardest known naturally occurring material, scoring 10 on the old Mohs scale of mineral hardness. The material boron nitride, when in a form structurally identical to diamond, is nearly as hard as diamond; a currently hypothetical material, beta carbon nitride, may also be as hard or harder in one form. Furthermore, it has been shown 1 (http://www.mrs.org/publications/jmr/jmra/articles/1997/nov/p03109.pdf) 2 (http://www.mtu-net.ru/nanoscan/files/article_03.pdf) that ultrahard fullerite (C60) (not to be confused with P-SWNT Fullerite) when testing diamond hardness with a scanning force microscope can scratch diamond. In turn, using more accurate measurments, these values are now known for diamond hardness. A Type IIa diamond (111) has a hardness value of 167 GPa (±6) when scratched with an ultrahard fullerite tip. A Type IIa diamond (111) has a hardness value of 231 GPa (±5) when scratched with a diamond tip which leads to hypothetically inflated values.

 

The diamond derives its name from the Greek adamas, "untameable" or "unconquerable", referring to its hardness.

Diamonds typically crystallize in the cubic crystal system and consist of tetrahedrally bonded carbon atoms. A second form called lonsdaleite with hexagonal symmetry is also found. The local environment of each atom is identical in the two structures. Cubic diamonds have a perfect octahedral cleavage, which means that they have four cleavage planes. Diamonds occur most often as euhedral or rounded octahedra and twinned octahedra known as macles. Other forms include dodecahedra and cubes. Diamonds are commonly found coated in nyf, a gum-like skin. Their fracture may be step-like, conchoidal (shell-like, similar to glass) or irregular.

 

Toughness


Unlike hardness, which only denotes resistance to scratching, diamond's toughness is only fair to good. Toughness relates to its ability to resist breakage from falls or impacts. Particular cuts of diamonds are more prone to breakage, and thus may be uninsurable by reputable insurance companies. The culet is a facet designed exclusively to resist breakage. Extremely thin, or very thin girdles are also prone to much higher breakage.

 

Optical properties


The luster of a diamond is described as adamantine, which simply means diamond-like. Some diamonds exhibit fluorescence of various colors under long wave ultra-violet light, but generally bluish-white, yellowish or greenish fluorescence under X-rays. Some diamonds, particularly Canadian diamonds, show no fluorescence. Diamonds have an absorption spectrum consisting of a fine line in the violet at 415.5 nm. Colored stones show additional bands. Brown diamonds show a band in the green at 504 nm, sometimes accompanied by two additional weak bands also in the green.

 
Adamas Gemological Laboratory (http://www.gis.net/~adamas) makes spectrophotometer machines that can distinguish natural, artificial, and color-enhanced diamonds. Diamond has an index of refraction of 2.42 in the visible spectrum.
 
Electrical properties
 
Except for most natural blue diamonds which are semiconductors, diamond is a good electrical insulator. Natural blue diamonds recently recovered from the Argyle mine in Australia have been found to owe their color to an overabundance of hydrogen atoms: these diamonds are not semiconductors. Natural blue diamonds containing boron and synthetic diamonds doped with boron are p-type semiconductors. If an n-type semiconductor can be synthesized, electronic circuits could be manufactured of diamond. Worldwide research is in progress, with occasional successes reported, but nothing definite. In 2002 it was reported in the journal Nature that researchers have succeeded in depositing a thin diamond film on a diamond surface which is a major step towards manufacture of a diamond chip. In 2003 it was reported that NTT developed a diamond semiconductor device[1] (http://www.eetimes.com/at/hpm/news/OEG20030822S0005). In April of 2004 Nature reported that below the superconducting transition temperature 4 K, boron-doped diamond synthesized at high temperature and high pressure is a bulk, type-II superconductor[2] (http://www.nature.com/nature/journal/v428/n6982/pdf/nature02449.pdf). In October of 2004 superconductivity was found to occur in heavily boron-doped microwave plasma-assisted chemical vapor deposition (MPCVD) diamond below the superconducting transition temperature of 7.4 K[3] (http://content.aip.org/APPLAB/v85/i14/2851_1.html)

 
Thermal properties
 
Unlike most electrical insulators, diamond is a good conductor of heat because of the strong covalent bonding within the crystal. Most natural blue diamonds contain boron atoms which replace carbon atoms in the crystal matrix, and also have high thermal conductance. Specially purified synthetic diamond has the highest thermal conductivity (2000–2500 W/(m·K), five times more than copper) of any known solid at room temperature. Because diamond has such high thermal conductance it is already used in semiconductor manufacture to prevent silicon and other semiconducting materials from overheating.
 
 
 
 
 
 
 
 
 
 

The Allnatt Diamond Centenary Diamond Cullinan Diamond The Deepdene Dresden Green Diamond The Golden Jubilee The Heart of Eternity Diamond Hope Diamond Hortensia Diamond Idol's Eye Koh-i-Noor The Moussaieff Red Diamond The Ocean Dream Diamond The Orloff Portuguese Diamond Premier Rose Diamond The Pumpkin Diamond The Regent Diamond Star of Africa The Steinmetz Pink Diamond The Taylor-Burton Diamond The Tiffany Yellow Diamond The Sancy Vargas Synthetic diamond Conflict diamond

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