The word “diamond” is derived from the Greek “adamas” which means untameable. Already in the first century AD, the diamond was mentioned in the Natural History of Plinio the Elder, who considered it the most precious stone and harder than all the other stones. For this reason it assumes an important symbolic significance and is linked to the capacity to ward away evil via its incorruptibility.
The diamond represents one of many forms of carbon. In this case the atomic composition of carbon is made in the geometric shape of an octahedron.
Origin of the diamond
The diamond was formed millions of years ago in the earth’s crust and only thanks to volcanic eruptions emerged on the earth’s surface in kimberlite. The erosion and crumbling away of kimberlite freed diamonds of various sizes, colours and purities, which would later be sorted in specialised centres. One of the most important diamonds discovered in the kimberlite deposits was the Cullinan, found in 1905 at the Premier mine.
The Cullinan diamond weighed 3,025 carats in its rough form, equivalent to 605 grammes. After it was cut around 100 stones were obtained, of which the most important weighed 516.5 carats.
The chemical composition of the diamond
The structure of a diamond is composed of crystals that will form an octahedron. Based on the gemmation of the carbon crystals, various shapes are found, whether triangular, or more rarely cubic shapes.
As mentioned in the previous chapter, the diamond is a crystal composed of carbon atoms that combine in the structure of a tetrahedron. Among the characteristics that are most important, one can mention the fusion point which is 3,820 degrees Kelvin, the index of refraction of light, and the hardness index which is equal to 10 on the Mohs scale.
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Chemical-physical properties
The diamond is a transparent crystal composed of carbon atoms in a tetrahedron structure. Diamonds have diverse applications, thanks to the exceptional physical characteristics of the material from which they are made. The most relevant characteristics are extreme hardness, the index of refraction of light, high thermal conductivity, with a fusion point of 3,820 K.
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Hardness
The diamond is the hardest known mineral. Its hardness as measured on the Mohs scale (an empirical gauge of the hardness of materials) is equal to 10, and is due to the presence of extended links throughout its atomic structure. This explains the exceptional characteristics of stability of this structure, and of similar structures with similar characteristics, for example boron nitride.
Among materials of synthetic origin are ADNR (Aggregated Diamond Nanorods), a form of carbon synthesised for the first time in 2005 by researchers of the German university of Bayreuth, Natalia Dubrovinskaia, Leonid Dubrovinsky, and Falko Langenhorst. Beside having other notable properties, this material turned out to be harder than a natural diamond.
Not all diamonds have the same hardness. The hardest diamonds are from the area of New England in New South Wales (Australia.) These diamonds are generally small, have a perfect or semi-perfect octahedron shape, and are used to polish other diamonds. Their hardness is considered to be the result of the way in which the crystal grew, in a single phase. Most other diamonds demonstrate crystal growth in successive phases, with inclusions of impurity and the formation of defects in the crystalline lattice and consequent diminution of the characteristics of hardness. -
Conductivity
Some blue diamonds are natural semiconductors, unlike other diamonds which are excellent electrical insulators. The diamond exposed to the air shows in some conditions a conductor behavior on its surface. The phenomenon was discovered by Maurice Landstrass and K. V. Ravi in 1989.
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Placing a date on a diamond
The carbon-14 method is not efficient in this case, because it is limited to carbon of biological origin. Also techniques of geochronology, for example, the uranium-lead method, are inefficient in this respect, because of the chemical purity of the diamond.
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Chemical-physical properties
The diamond is a transparent crystal composed of carbon atoms in a tetrahedron structure. Diamonds have diverse applications, thanks to the exceptional physical characteristics of the material from which they are made. The most relevant characteristics are extreme hardness, the index of refraction of light, high thermal conductivity, with a fusion point of 3,820 K.
-
Hardness
The diamond is the hardest known mineral. Its hardness as measured on the Mohs scale (an empirical gauge of the hardness of materials) is equal to 10, and is due to the presence of extended links throughout its atomic structure. This explains the exceptional characteristics of stability of this structure, and of similar structures with similar characteristics, for example boron nitride.
Among materials of synthetic origin are ADNR (Aggregated Diamond Nanorods), a form of carbon synthesised for the first time in 2005 by researchers of the German university of Bayreuth, Natalia Dubrovinskaia, Leonid Dubrovinsky, and Falko Langenhorst. Beside having other notable properties, this material turned out to be harder than a natural diamond.
Not all diamonds have the same hardness. The hardest diamonds are from the area of New England in New South Wales (Australia.) These diamonds are generally small, have a perfect or semi-perfect octahedron shape, and are used to polish other diamonds. Their hardness is considered to be the result of the way in which the crystal grew, in a single phase. Most other diamonds demonstrate crystal growth in successive phases, with inclusions of impurity and the formation of defects in the crystalline lattice and consequent diminution of the characteristics of hardness. -
Conductivity
Some blue diamonds are natural semiconductors, unlike other diamonds which are excellent electrical insulators. The diamond exposed to the air shows in some conditions a conductor behavior on its surface. The phenomenon was discovered by Maurice Landstrass and K. V. Ravi in 1989.
-
Placing a date on a diamond
The carbon-14 method is not efficient in this case, because it is limited to carbon of biological origin. Also techniques of geochronology, for example, the uranium-lead method, are inefficient in this respect, because of the chemical purity of the diamond.
Diamonds in jewellery
The diamond became important in jewellery due to its capacity to preserve its polished appearance for long periods. Only a diamond is capable of scratching another diamond, and so it can be worn every day without worrying about suffering any damage.
The round shape of the diamond is the most famous and most widely used in the world of jewellery. The brilliant diamond cut indicates a diamond with 57 facets. The great popularity of this cut has led to a misunderstanding: the public tends to identify the terms brilliant and diamond as if they are the same thing. In practice the term brilliant, if used alone, only identifies the diamond with the round cut. There are, however, many other precious stones that can have a brilliant cut, for example topaz, rubies and sapphires.
