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Diamond is extremely strong owing to its crystal structure, known as diamond cubic, in which each carbon atom has four neighbors covalently bonded to it. Bulk cubic boron nitride (c-BN) is nearly as hard as diamond. Diamond reacts with some materials, such as steel, and c-BN wears less when cutting or abrading such material. [4]
From the size of the resulting indentation, a Vickers hardness value for the material can be determined. Diamond's great hardness relative to other materials has been known since antiquity, and is the source of its name. This does not mean that it is infinitely hard, indestructible, or unscratchable. [26]
In 2001, a diamond-like-structured c-BC 2 N was synthesized at pressures >18 GPa and temperatures >2,200 K by a direct solid-state phase transition of graphite-like (BN) 0.48 C 0.52. The reported Vickers and Knoop hardnesses were intermediate between diamond and c-BN, making the new phase the second hardest known material. [39]
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This was long believed to refer to diamond, but is now thought more likely to mean other hard minerals such as corundum or spinel. [b] Diamonds eventually spread throughout the world, even though India had remained the only major source of the gemstone until diamonds were discovered in Brazil in 1725. [10]
Diamond is the ultimate abrasive, but graphite is soft and is a very good lubricant. Diamond is an excellent electrical insulator, but graphite is an excellent conductor. Diamond is an excellent thermal conductor, but some forms of graphite are used for thermal insulation (for example heat shields and firebreaks).
Diamond manufacturers make a groove in the diamond with a laser or saw or another diamond, and then split the diamond by placing a steel blade in the groove and giving a gentle tap. [8] Cleavage can be along any of the four planes parallel to the faces of an octahedral diamond (i.e. perpendicular to body diagonals of the unit cell).
Drypoint is a printmaking technique of the intaglio family, in which an image is incised into a plate (or "matrix") with a hard-pointed "needle" of sharp metal or diamond point. In principle, the method is practically identical to engraving .