Diamond, description, features, properties and origin.
Diamond is a solid allotropic form of carbon atoms which have a cubic face-centered crystal lattice.
Diamond, characteristics, description, crystal lattice, chemical composition
The formation and origin of diamonds
Mechanical, optical, chemical and other properties of diamond
Physical properties of diamond
Evaluation of a diamond as a jewelry stone
Diamond, characteristics, description, crystal lattice, chemical composition:
Diamond (from the ancient Greek. ἀδάμας “enduring” through Arab. ألماس [’almās] and tour. elmas) – mineral, cubic allotropic form of carbon. Chemical formula of diamond is C.
Along with graphite, diamond , there are many allotropic forms of carbon. For example, graphene, fullerene, carbon nanotubes , etc. properties of the substances are completely different from each other.
Diamond is the hardest natural material on Earth.
Diamond is a rare, but very widespread mineral. To date, diamonds have been found on all continents, including Antarctica.
Diamond is a solid allotropic form of carbonatoms which have a cubic face-centered crystal lattice. Thus, each carbon atom in the structure of diamond is situated in the centre of a tetrahedron whose vertices are the four nearest atom.
Thus, in diamond each carbon atom bonded to four other atoms. In the diamond when formed sp3 hybrid orbitals. Such a connection is the most durable. That is a strong bond of carbon atoms and no free electrons explains the high hardness of diamond. Of all known substances, diamond also has the highest number of atoms per unit volume, therefore it is simultaneously the hardest and least compressible.
On the contrary, in graphite, the other allotropic form of carbon, every carbon atom connected to three atoms, similar atoms and has one free electron. In graphite inter-atomic bonding formed by sp2 hybrid orbitals. Connection between carbon atoms in graphite are formed in the same plane. Communication between the planes of graphite are weak. This causes a high softness of graphite and the property, layers of graphite easily separate (peel off) from each other.
Under normal conditions (i.e. room temperature and normal pressure) and high pressures diamond can exist indefinitely. At room temperature and pressure, other solid form of carbon known as graphite also is chemically stable form, but the diamond is almost never turning into her. And only in vacuum or in inert gas at elevated temperatures – at 2000 ° diamond gradually turns into graphite.
Diamonds come in all different colors and shades ranging from steel grey, white to brown and black. Rare colorless and transparent stones. This is because the natural diamond may contain a small amount of defects or impurities (about one per million carbon atoms). Small amounts of defects or impurities color diamond blue (boron impurities), yellow (nitrogen impurities), brown (lattice defects), green (radiation exposure), purple, pink, orange or red color. However, chemically pure and structurally perfect diamond is transparent and has no tint or color.
Diamond also has relatively high optical dispersion (ability to disperse light of different colors).
The hardness of diamond and its high optical dispersion contributes to its use as gemstone. Unlike many other gems it is well suited to daily wear because of its resistance to scratching. To scratch a diamond is another diamond.
Faceted diamond is called a diamond.
Diamond consists of pure carbon. In small quantities it contains various impurities of other chemical elements (boron, nitrogen, aluminum, silicon, calcium, magnesium, etc.).
The formation and origin of diamonds:
Most natural diamonds are between the ages of 1 billion to 3.5 billion years. Many of them were formed at depths of 150 to 250 kilometers in the mantle of the Earth, although some of them were formed at a depth of about 800 kilometers.
Under high pressure and temperature of carbon-containing fluids dissolve minerals in the rock and replaced them with diamonds.
Diamonds were formed from this liquid, or by restoring oxidized carbon (e.g., CO2 or CO3) or by oxidation of the recovered phase such as methane.
Much later (tens – hundreds of millions of years ago) they were brought to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites.
Mechanical, optical, chemical and other properties of diamond:
diamond is a solid form of pure carbon. Hardness on the Mohs scale 10,
the hardness of diamond depends on its purity, absence of defects in the crystal lattice and orientation. Hardness is higher for flawless, pure crystalsoriented in the direction of the longest diagonal of the cubic diamond lattice. Therefore, diamonds can be scratched and to be processed only by other diamonds
of all known substances, diamond has the highest number of atoms per unit volume, therefore it is simultaneously the most solid, and least compressible. A diamond with a low compression ratio,
– has a high density of 3.47 to 3.55 g/cm3,
– has a fragile, easily splitting,
– the fracture is conchoidal,
– has a large refractive index and a relatively high optical dispersion (ability to disperse light of different colors). These properties force applied in the processing of diamond faces to Shine, playing on the light,
– possesses the highest conductivity among all solid bodies 900-2300 W/(m·K). Because of this, the diamond feels cold
– the diamond has a very low coefficient of friction on metal,
– has the highest modulus of elasticity,
– in the air diamond burns at 850-1000 °C and a stream of pure oxygen burns with a weak blue flame at 720-800 °C, fully turning into carbon dioxide,
under the action of sunlight and under the action of cathode, ultraviolet and x-rays diamonds begin to luminesce glow different colors. It is this peculiar property of the diamond allows it to identify the breed
the diamond surface is hydrophobic and lipophilic, i.e. the diamond is not wetted by water, and well wetted by oil and grease. This property is used to distinguish diamond from a fake. Fat on the fake does not wet the surface completely, and gathers in small droplets. In addition, the diamond, greased, sticks to the glass, and the fake – no,
– diamonds are chemically stable. At room temperature they do not react with acids and alkalis. The surface of the diamond can be oxidized in the temperature of air above 850 °C. the Diamond also reacts with fluorine gas at temperatures above 700 °C,
– refraction of diamond is such that, by placing a colorless crystal to a page of printed text to read will not work. This characteristic of a diamond allows to distinguish fake from the original. Also if you look through a diamond in the sun, it will be visible, only the dull point,
– under the influence of radioactive radiation the diamond changes color on the rich green color.
Physical properties of diamond:
|Name of the parameter:||Value:|
|The bond length C–C, nm||0,15|
|Density, g/cm2||from of 3.47 to 3.55|
|Melting point (at pressure of 11 GPA), OS||3700-4000 °C|
|Thermal conductivity, W/(m·K)||from 900 to 2300|
|The refractive index||from 2,417 to 2,419 (in yellow),
in other colors – from 2,402 (red) to 2,465 (the color purple).
|Hardness (Mohs scale)||10|
|Hardness, GPa||from 70 to 150|
The main types of cut of a diamond are:
– round (with a standard 57 facets),
– fantasy, which includes such cuts as “oval”, “pear”, “Marquise”, “Princess”, “radiant”, “heart”, “square”, “emerald”, “triangle” and other types.
The shape of the cut of a diamond depends on the shape of the original diamond crystal.
Evaluation of a diamond as a gemstone:
Faceted diamond is called a diamond (from the French. brillant “brilliant, shining”). He is given a special shape, maximum reveals its natural Shine.
Only 60% of diamonds mined are suitable for jewelry processing. All other diamonds find application in various industries.
All diamonds are evaluated according to the “4 C”:
– cut (cut),
– clarity (purity),
– color (color)
and carat (weight in carats), which allows to determine how the stone is close to perfection.
In the cut (cut) diamond is valued by its quality: how verge geometrically accurate and proportional to each other. Ideal cut has a letter “A”, then B, C, d — in descending order of quality. In the international system (GIA, Gemological Institute of America) ideal cut is designated as Excellent, and in descending order of quality (Very Good, Good, Fair, Bad).
Purity (clarity ) is perhaps the most significant indicator of the quality of diamonds: it is expressed in the presence or absence of defects in the stone or foreign inclusions. Diamonds without flaws are called diamond pure water.
The color of the diamond is also important. Particularly prized diamonds are green, purple and black colors. Such diamonds are very rare.
Weight of diamonds is measured in carats: 1 carat is equal to 0.2 grams. The greater the mass of a diamond, so it is more expensive.
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