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The planes of weakness (cleavage planes) in a diamond are in four directions, following the faces of the octahedron. In graphite, carbon atoms are contained in layers in a hexagonal pattern where the covalent bonds are shorter (and thus even stronger) than those of diamond.
Like ballas diamond, carbonado lacks cleavage planes and its specific gravity varies widely from 2.9 to 3.5. Bort diamonds, found in Brazil, Venezuela, and Guyana, are the most common type of industrial-grade diamond. They are also polycrystalline and often poorly crystallized; they are translucent and cleave easily. [8]
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 before faceting them. [34] "Impact toughness" is one of the main indexes to measure the ...
Twinning causes natural lines, planes or cross-grains in a diamond. Graining can't be removed during the polishing process of a diamond as it is a natural plane within the diamond. Cross-graining also makes the polishing process extremely difficult for diamond cutters as a diamond only cuts against its natural grain lines and never with the grain.
The diamond is currently set in the Crown of Queen Elizabeth The Queen Mother. There are multiple conflicting legends on the origin of the diamond. [9] However, in the words of the colonial administrator Theo Metcalfe, there is "very meagre and imperfect" evidence of the early history of the Koh-i-Noor before the 1740s. [10]
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). [9]
Diagram of the pre-1852 cut Koh-i-Noor. [49] Fig I. The shaded area is the base. Fig II. A: flaw; B and C: notches cut to hold the stone in a setting; D: flaw created by fracture at E; F: fracture created by a blow; G: unpolished cleavage plane; H: basal cleavage plane. Fig III. The opposite side shows facets and peak of the "Mountain of Light"
Some directions and planes are defined by symmetry of the crystal system. In monoclinic, trigonal, tetragonal, and hexagonal systems there is one unique axis (sometimes called the principal axis) which has higher rotational symmetry than the other two axes. The basal plane is the plane perpendicular to the principal axis in these crystal ...