Qualitative composition of the diamond. Formula of diamond, its chemical and physical properties. Diamond Extraction Technologies

DIAMOND (Turk. almas, from Greek adamas - indestructible, invincible * a. diamond; n. Diamant; f. diamant; and. diamante) - crystalline cubic modification of native.

Structure of a diamond. The unit cell of the spatial crystal lattice of diamond is a face-centered cube with 4 additional atoms located inside the cube (Fig.).

Unit cell edge size a 0 = 0.357 nm (at t = 25°C and P = 1 atm). shortest distance between two neighboring atoms C = 0.154 nm. The carbon atoms in the structure of diamond form strong covalent bonds directed at an angle of 109°28" relative to each other, making diamond the hardest substance known in nature. In the band structure of diamond, the band gap for non-vertical transitions is 5.5 eV, for vertical - 7.3 eV, valence band width 20 eV Electron mobility mn = 0.18 m 2 /V.s, holes mr = 0.15 m 2 /V.s.

Morphology of the diamond. Diamond crystals have the shape of an octahedron, rhombic dodecahedron, cube and tetrahedron with smooth and lamellar-stepped faces or rounded surfaces, on which various accessories are developed. Characterized by flattened, elongated and complexly distorted crystals of simple and combined shapes, twins of intergrowth and intergrowth according to the spinel law, parallel and randomly oriented intergrowths. Varieties of diamond are polycrystalline formations: bead - intergrowths of numerous small faceted crystals and grains of irregular shape, gray and black; ballas - spherulites of a radially radiant structure; carbonado - cryptocrystalline, dense, with an enamel-like surface or slag-like porous formations, consisting mainly of submicroscopic (about 20 microns) diamond grains, closely fused with each other. The size of natural diamonds ranges from microscopic grains to very large crystals weighing hundreds and thousands of carats (1 carat = 0.2 g). The mass of mined diamonds is usually 0.1-1.0 carats; large crystals (over 100 carats) are rare. The table shows the world's largest diamonds extracted from the bowels.

Chemical composition. The diamond contains impurities Si, Al, Mg, Ca, Na, Ba, Mn, Fe, Cr, Ti, B number. With the help of a-particles of radioisotope H, N, O, Ar and other elements. is the main impurity that has a great influence on physical properties diamond. Diamond crystals that are opaque to ultraviolet radiation are called type I diamonds; all others are type II. The nitrogen content in the vast majority of type I diamond crystals is about 0.25%. Less common are nitrogen-free diamonds of type II, in which the admixture of nitrogen does not exceed 0.001%. Nitrogen enters the structure of diamond isomorphically and forms, alone or in combination with structural defects (vacancies, dislocations), centers responsible for color, luminescence, absorption in the ultraviolet, optical, infrared and microwave regions, the nature of X-ray scattering, etc.

Physical properties. Diamonds can be colorless or with a subtle color tint, as well as to varying degrees of clearly colored yellow, brown, mauve, green, blue, blue, milky white and gray (to black) colors. When irradiated with charged particles, the diamond acquires a green or blue color. The reverse process - the transformation of a colored diamond into a colorless one - has not yet been carried out. Diamond is characterized by strong brilliance, a high refractive index (n = 2.417) and a pronounced dispersion effect (0.063), which causes a multi-colored play of light in. As a rule, anomalous birefringence appears in diamond crystals due to stresses arising from structural defects and inclusions. Diamond crystals are transparent, translucent or opaque depending on saturation with microscopic inclusions of graphite, other minerals and gas-liquid vacuoles. When illuminated with ultraviolet rays, a significant part of transparent and translucent diamond crystals luminesces blue, light blue and less often yellow, yellow-green, orange, pink and red. Diamond crystals (with rare exceptions) luminesce when exposed to X-rays. The glow of a diamond is excited by cathode rays and when bombarded by fast particles. After excitation is removed, an afterglow of varying duration (phosphorescence) is often observed. Diamond also exhibits electro-, tribe-, and thermoluminescence.

Diamond, as the hardest substance in nature, is used in a variety of tools for sawing, drilling and processing all other materials. Relative on the Mocca 10 scale, the maximum absolute microhardness measured by the indenter on the face (111), 0.1 TPa. The hardness of diamond on different crystallographic faces is not the same; the hardest is the octahedral face (111). Diamond is very brittle, has a very perfect cleavage along the (111) face. Young's modulus 0.9 TPa. The density of transparent diamond crystals is 3515 kg / m 3, translucent and opaque - 3500 kg / m 3, for some Australian diamonds - 3560 kg / m 3; at the side and carbonado due to their porosity can be reduced to 3000 kg/m 3 . The clean surface of diamond crystals is high (contact angle 104-105°). In natural diamonds, especially in diamonds from alluvial deposits, the thinnest films are formed on the surface, which increase its wettability.

Diamond is a dielectric. The specific resistance r for all type I nitrogen diamond crystals is 10 12 -10 14 Ohm.m. Among nitrogen-free diamonds of type II, sometimes there are crystals in which r is below 10 6 Ohm.m, sometimes up to 10-10 -2. Such diamonds have r-type conductivity and photoconductivity, and under the same conditions, the photocurrent in type II diamond is an order of magnitude greater than the photocurrent excited in type I diamond. Diamond is diamagnetic: the magnetic susceptibility per unit mass is 1.57.10 -6 SI units at 18°C. Diamond is resistant to all acids even at high temperatures. In melts of alkalis KOH, NaOH and other substances in the presence of O, OH, CO, CO 2 , H 2 O, oxidative dissolution of diamond occurs. Ions of some elements (Ni, Co, Cr, Mg, Ca, etc.) have catalytic activity and accelerate this process. Diamond has a high thermal conductivity (especially nitrogen-free type II diamonds). At room temperature their thermal conductivity is 5 times higher than Cu, and the coefficient decreases with increasing temperature in the range of 100-400 K from 6 to 0.8 kJ / m.K. The polymorphic transition of diamond into at atmospheric pressure occurs at a temperature of 1885±5°C throughout the entire volume of the crystal. The formation of graphite films on the surface of faces (III) of diamond crystals under the influence can occur starting from 650°C. In air, diamond burns at a temperature of 850°C.

Prevalence and origin. Diamonds have been found in meteorites, impact rocks associated with meteorite craters (astroblemes), in and small deep mantle rocks of pregithic and eclogitic compositions located in them, as well as in secondary sources — placers of different age and genesis ( , etc. ). There is no consensus on the origin of diamonds. Some scientists believe that diamonds crystallize in the kimberlite pipes themselves during their formation or in intermediate chambers that occur at shallow (3-4 km) depths (subvolcanic chambers). Others believe that diamonds are formed at great depths in the parent kimberlite melt and continue to crystallize as it rises to the top. The idea that diamonds are genetically related to diverse rocks and are removed from them along with other xenogenic material found in kimberlites is most justifiably developed. There are other ideas about the genesis of diamond (for example, crystallization at low pressures using carbon from abyssal origin and carbonates of host rocks).

Diamond deposits. Diamond-bearing kimberlite rocks and alluvial deposits formed due to their erosion are of industrial importance. Kimberlites are found mainly on ancient and; they are characterized mainly by tubular bodies, as well as huskies and. The dimensions of kimberlite pipes are from one to several thousand meters in cross section (for example, the Mwadui pipe in Tanzania with parameters of 1525x1068 m). More than 1500 kimberlite bodies are known on all platforms, but only a few diamonds have industrial content. Diamonds are distributed extremely unevenly in kimberlites. Pipes with a diamond content of 0.4 carats/m 3 and above are considered industrial. In exceptional cases, when the pipes contain an increased percentage of high-quality diamonds, exploitation with a lower content, for example, 0.08-0.10 carats/m 3 (Jägersfontein in South Africa), can be profitable. Kimberlites are dominated by crystals 0.5-4.0 mm in size (0.0025-1.0 carats). Their weight fraction is usually 60-80% of the total mass of recovered diamonds. Reserves at individual deposits amount to tens of millions. The largest primary diamond deposits have been explored in Tanzania, Lesotho, Sierra Leone and others.

Enrichment. In alluvial deposits, the rock is first washed in order to remove the binding clay mass and separate large clastic material; the isolated loose material is divided into four classes: -16+8, -8+4, -4+2, -2+0.5 mm. produced by gravitational methods (wet and air, enrichment in heavy suspensions, in concentration bowls). To extract small diamonds and diamond chips, film and foam are used with preliminary cleaning of the surface. Reagents: amines, aeroflots, fatty acids, kerosene, cresyl acid. To extract diamonds, the fat process (for grains with a particle size of 2–0.2 mm) is most widely used, based on the selective ability of diamonds to stick to fatty surfaces. Vaseline, petroleum, autol and its mixture with paraffin, oleic acid, nigrol, etc. are used as a fat coating. poor conductor of electricity). An X-ray luminescent method is used to extract relatively large diamonds, based on the ability of diamond crystals to luminesce (X-ray luminescent machines).

Application. Diamonds are divided into jewelry and technical. The former are highly transparent. The most valuable are colorless diamonds (" pure water") or with a good color. All other mined diamonds, regardless of their quality and size, are classified as technical diamonds. In the CCCP, diamonds are sorted according to technical specifications, which are supplemented as the areas of application of diamonds expand. Depending on the types and purpose, rough diamonds by quality classified into categories, in each category there are groups and subgroups that determine the size, shape, specific conditions for the appointment of diamond crystals.About 25% of diamonds mined in the world are used in the jewelry industry to make diamonds.

Having exceptionally high hardness, diamonds are indispensable for the manufacture of various tools and devices (and, indenters for measuring the hardness of materials, drawing dies, needles for profilometers, profilographs, pantographs, drills, cutters, applied stones for marine chronometers, glass cutters, etc.). Diamonds are widely used for the manufacture of abrasive powders and pastes, for refilling diamond saws. Some metals, semiconductor materials, ceramics, building reinforced concrete materials, crystal, etc. are processed with diamond tools. Due to the combination of a number of unique properties, diamonds can be used to create electronic devices designed to operate in strong electric fields, at high temperatures, under conditions advanced level radiation, in aggressive chemical environments. On the basis of diamonds, nuclear radiation detectors, heat sinks in electronic devices, thermistors and transistors have been created. The transparency of diamonds for infrared radiation and the weak absorption of X-rays make it possible to use them in infrared receivers, in chambers for studying phase transitions at high temperatures and pressures.

Synthetic diamonds. In the mid 50s. began the development of industrial synthesis of technical diamonds. Synthesized mainly small single crystals and larger polycrystalline formations such as ballas and carbonado. The main methods of synthesis are: static - in the metal-graphite system at high pressures and temperatures; dynamic - polymorphic transition of graphite in diamonds under the influence of a shock wave; epitaxial - the growth of diamond films on diamond seeds from gaseous hydrocarbons at low pressures and temperatures of about 1000 ° C. Synthetic diamonds are used in the same way as natural industrial ones. The total production of synthetic diamonds significantly exceeds the production of natural ones.

Diamond is the hardest mineral in the world and is an allotropic form of carbon. Diamond's closest relative is graphite, the same material used to make pencil leads.

The mineral got its name from the ancient Greek word adamas, which means "invincible" in translation.

Characteristics and types

Diamonds are minerals, the main characteristics of which include the following:

The highest hardness ( 10 on the Mohs hardness scale);

At the same time, high brittleness;

The highest thermal conductivity among solids (900-2300 c.u.)

Does not conduct electricity;

Melting point - 4000ºC;

Combustion temperature - 1000 ºC;

Has luminescence.

Diamond is 96-98% carbon. The rest is impurities of various chemical elements, which give a shade to the mineral. Most natural diamonds are yellowish or brownish in color. Blue, blue, green, red and black diamonds are also found in nature.

After processing and cutting, the color coating disappears, so the vast majority of diamonds are colorless. Colored diamonds are extremely rare. Among the most famous are: Dresden (green), Tiffany diamond (yellow) and Porter Rhodes (blue).

One of the methods for determining the authenticity of a diamond is quite simple: a line is drawn along the surface with a special felt-tip pen containing bold ink. If the line remains solid, then the diamond is real. On fake ones, the line crumbles into droplets.

Deposits and production

(An incredible quarry in which diamonds have been mined for a very long time is located in the village of Mir, Sakha, Yakutia)

Diamond deposits have been found on every continent except Antarctica. In nature, diamonds occur in the form of placers, but most of them are contained in kimberlite pipes. Kimberlite pipes are a kind of "holes" in the earth's crust, which are formed during the explosion of gases. According to experts, these pipes contain up to 90% of all diamonds on earth.

The richest diamond deposits are in Botswana, Russia, Canada, Australia and South Africa. More than 130 million carats of diamonds (about 30 tons) are mined annually in the world. Russia ranks first in the world in diamond mining (29% of world production), yielding to Botswana only in the value of the minerals found.

In Russia, the first diamond was found in 1829 in the Perm region. Now this field is called "Diamond Key". Later, deposits were discovered in Siberia and the Arkhangelsk region. The largest deposit is located on the border of the Krasnoyarsk Territory and Yakutia. Presumably, it contains about a trillion carats.

In 2015, a new type of diamond deposit was discovered in Kamchatka. These are the so-called "Tolbachin" diamonds, which were found in the hardened lava of the volcano. In just a few samples taken here, several hundred diamonds have already been found.

The largest diamond was found in 1905 in South Africa. It's called The Cullinan. Its weight is 3106 carats. 96 small and 9 large diamonds were obtained from the diamond, the largest of which is the "Star of Africa" ​​(530 carats). This diamond now adorns the scepter of the English monarchs and is kept in the Tower.

In 1939, the Russian physicist O. Leipunsky first obtained a synthetic diamond. And since 1963, serial production of synthetic diamonds has been launched, which are widely used in engineering and jewelry.

Application of diamonds

The vast majority of natural diamonds (up to 70%) are used in jewelry - for jewelry. Almost 50% of the world's diamond production belongs to the De Beers company, which holds a monopoly by setting high prices for 1 carat. IN Lately The Russian company "Alrosa", leading the development and production in 9 countries of the world, is knocked out as a leader.

Application in industry:

For the manufacture of knives, saws, cutters, drill columns, glass cutters, etc.;

As an abrasive in the manufacture of grinding machines, circles;

In the watch industry;

In the nuclear industry;

In optics;

In the manufacture of quantum computers;

in the production of microelectronics.

The question of what a diamond is sometimes frankly misleads people, forcing their imagination to imagine magic game sun glare on its edges.

This crystal, which has been in the hands of a professional jeweler, is initially not so beautiful.

Having met a faceless mineral on its way, few people will believe that this is a future jewel.

What is a diamond and what does it look like

In fact, diamond is a natural mineral that arose in the process of compacting carbon at great depths under conditions of high temperature and high pressure.

It has a transparent, dense and durable structure that allows it to exist for an unlimited amount of time. It also has a high thermal conductivity compared to other substances found in nature.

Externally, the raw material has a completely unattractive appearance with a rough surface, various inclusions and a dull color due to foreign particles stuck to it. It is usually represented in the form of a dodecahedron, an octahedron and a cube.

Origin of diamond

People have known about the diamond for more than one millennium. The first information about the "magic" stone is mentioned in the Indian tablets, which speak of a heavenly gift, which includes five natural principles. People collected and processed it, decorating them with divine statues and attributing mystical properties to them.

Naturally, no one thought that it was thanks to the multi-ton pressure of rocks with boiling lava inside, with exorbitant temperature, that conditions were created for its occurrence, with magma transported to the surface.

In other words, such a carbon rock originates only in igneous mountainous places, kimberlite pipes - volcanoes. Sometimes, during the destruction of rocks, its placers are found on sea and river banks.

It was thanks to the inquisitive craftsmen who appeared in the old days that the mineral, through trial and error, was presented to the world in all its glory.

The first precious stone, which appeared in the world around 60 BC in India, became the 800 carat nugget "Kohinoor", a famous favorite of all the kings of the world.

It was originally an uncut yellow diamond that became pure white after being cut again at a later date.

Later, at the beginning of the 18th century, the first large occurrence of the carbon mineral was a place in Brazil, now the city of Diamantino.

But according to historical data, all the first carbon finds, among the alluvial deposits, lead to India, from which the most famous and largest jewels of the world came to light.

Types of diamonds

When evaluating a crystal Special attention is given not only to weight, but also to quality, the presence or absence of defects. In connection with the data obtained, they are divided into two types: jewelry and technical(unsuitable for jewelry).

After processing, they are also divided into types depending on the cut: pear-shaped, oval, round, tear-shaped, rectangular, and so on. Cut diamonds are called brilliants.

There is also a division of diamonds by color. Of course, everyone is accustomed to thinking that the only color is pure white and transparent, but in fact, other shades are inherent in it, depending on the place and condition of origin.

So, in addition to white, smoky, brown, pale yellow, and the most rare colors- red diamond, pink diamond, blue and cyan, bright yellow, green and black. Such a diamond is called fancy.

What is artificial diamond

There is a misconception that an artificial diamond is a high-quality fake for a natural, natural stone.

Actually, artificial material in no way inferior in its qualities to natural, and even exceeds the ideal beauty of the edges, although it was grown in other conditions, in compliance with all the rules.

Laboratory and natural crystals look equally unattractive until they are processed.

As early as the end of the 18th century, by experimental method, when burning a mineral, it was found that it consists of carbon. For scientists, this was the beginning of further lengthy experiments to create this breed in the laboratory, but the experiments were unsuccessful due to the lack of necessary equipment.

Only in the 20th century was the crystal lattice fully studied and scientists managed to synthesize a stone, observing the temperature and pressure force, but for the seed of which a natural crystal was still required.

The work on growing crystals has continued and continues with great enthusiasm. The knowledge of scientists and technologies are becoming more and more perfect every day, which allows an artificial diamond to become more and more similar to a natural gem in its crystal lattice and properties.

Physical and mechanical properties of diamond

Diamond is classified as a native element and has the simplest chemical formula C (carbon) and its own crystal lattice, consisting of a covalent bond between carbon atoms, which allowed it to take 10th place in hardness on the Mohs scale.

The covalent bond is the strongest, which makes it strong, but the structure of a substance can sometimes also allow metallic, ionic and hydrogen bonds. The connection has two subspecies - pi-bond and sigma-bond, of which the first subspecies is less strong.

Covalent sigma bonds connecting atoms and located one in each face of the crystal lattice provide the same distance between them, making the packing and structure denser. This ensures the hardness of the diamond, and in its characteristics there is the property of an excellent dielectric, low electrical conductivity.

Additional characteristics of carbon rock include:

• luminescence;
• low compressibility under all-round external pressure;
• fragility, the diamond is sensitive to sharp blows;
• the density is uneven, contributes to splitting along the edges;
• transparency;
• sensitivity to x-rays that break the hardness of the structure, giving the ability to glow in the blue and green spectral parts;

Intrinsic melting point for diamonds:

• melts at a temperature of 3700 to 4000 Celsius;
• with a mixture of gases in air, from 850 to 1000 degrees burns;
• turning on oxygen into carbon dioxide, the diamond burns with a blue flame from 700 to 800 degrees.

The mineral mined in nature is crystalline, with edges, split, with depressions and growths.

Diamond cutting

The only difference between a diamond and a brilliant is the cut, which gives natural stone noble and magical look. It is believed that the more ideally the shape is chosen and the more facets are applied, the brighter it shines and refracts the rays.

There are 8 main types of cuts:

• "A princess" - square shape and sharp corners
• "Round";
• "Marquise" - aristocratic, in the shape of a boat;
• "Pear" - teardrop shape;
• "Oval";
• "A heart";
• "Emerald" - rectangular and octagonal shape;
• "Usher" - square shape, but with big amount steps than "Emerald".

The process of transition from diamond to brilliant is very long and requires special skill:

1. To begin with, the crystal itself is inspected for the presence of defects, upon detection of which it is split to remove them.
2. The next step is peeling, where edges and corners are attached.
3. Grinding on a polishing wheel, on which diamond powder is poured, allowing you to bring the stone to an ideal state.
4. At the final stage, polishing takes place, which gives the diamond a gloss.

Good to know: the main thing in creating a diamond is the correctly superimposed edges. If you do not take into account refraction, the play of light, then the diamond will look dull, and such stones are considered marriage.

History of diamond mining in Russia

There is evidence that a diamond deposit in Russia was discovered in the 18th century on the territory of Yakutia and Siberia. Until 1917, only about 300 stones were found, but attempts did not stop there. At the time of the Great Patriotic War the development of mineral deposits was suspended and continued only after its completion.

A geological expedition sent to Yakutia in 1949 discovered the largest crystal deposit.

At this place, called Mirny, in the middle of the taiga, a city gradually grew up, whose population is involved in the extraction of ore.

The quarry in which it is mined is considered the deepest in the world. The depth of the quarry is about 530 meters, and the internal serpentine road reaches 8 kilometers.

Russian enterprises, in comparison with competitors in this business, produce about 97% of high-quality rough diamonds.

Where and how are diamonds currently mined?

Before the development of the industry, diamonds were mined in all countries only by diligent methods. Now in Russia, Angola, Canada, Botswana, South Africa and other countries that are engaged in ore mining, the extraction of the mineral is largely technically facilitated.

Mining mainly takes place in the places of the so-called ancient cratons, which contain lamproite and kimberlite pipes, and sometimes in roof rocks.

The largest deposits in Russia at the moment are Yakutsk and the Arkhangelsk region. Recently, small deposits of the mineral were discovered in the Perm Territory.

In terms of the percentage and quality of mined mineral stones, Russia remains the leading country.

Applications for diamonds

The diamond performs not only its decorative function, as an ornament, but also has its own practical application. Thanks to scientists and emerging technologies, discarded minerals have been used to benefit in other areas of life.

Since not all mined material is suitable for cutting under Jewelry, about 50% is rejected, then it is used for industrial and industrial needs:

• due to its ability to withstand temperature and power surges, diamond is used in telecommunications;
• used in the manufacture of medical devices and instruments (scalpels, implant);
• Almaz is added to the drill bit;
• with the property of low thermal conductivity, it is used in the production of electronics.

In terms of its popularity, the diamond is in first place among other jewelry, but this is not only due to the beauty brought to it by jewelers, but mostly because its extraordinary natural qualities are highly valued. Most likely, this crystal will never lose its primacy and will forever remain a mysterious and beautiful mystery.

Brief description: diamond, graphite and coal

Interconversions of diamond, graphite and coal

Turning - Graphite or Coal into Diamond

Get diamond from graphite

I got fake diamonds

Method for obtaining artificial diamonds

I found another one how to get artificial diamonds!

The problem of artificial diamonds

Turning graphite into diamond

The first artificial diamonds

Creation of artificial diamonds

How the diamond came into existence

Hypothesis of the deep birth of diamonds

Explosive hypothesis

Hypothesis of diamond birth in the cavitation regime

Diamond is a mineral that is nothing more than a modification of carbon. A pure diamond has a formula consisting of just one element. The stone has unique properties in nature, so the crystal lattice of diamond has interested scientists, and the structure of the substance continues to be studied.

An ideal diamond can be thought of as a giant carbon molecule. Scientists studied the composition of the mineral only at the end of the 18th century. From that moment, attempts began to artificially synthesize diamond in laboratories, but they were meaningless, since it was not possible to rebuild the crystal lattice from scratch.

Structure of a diamond

And the technology was not at such a level as to create conditions for the formation of a diamond. Only in the fifties of the twentieth century, scientists were able to synthesize diamond on their own. This was done by such countries as the USSR, the USA and South Africa.

The structure of matter

The whole snag and complexity of production lay in the unique structure of the diamond. Four types of bonds can form between atoms in chemistry:

• covalent;
• ionic;
• metal;
• hydrogen.

The strongest of these is the covalent bond. It also has its subspecies: sigma bonds and pi bonds. The second subspecies is less durable. There are several million carbon atoms in a diamond, which are linked together by covalent bonds.

The spatial arrangement of atoms and their compounds is called the crystal lattice. It is its structure that determines such a characteristic as the hardness of a substance. The unit cell of the diamond structure looks like a cube. That is, a diamond crystallizes in a cubic syngony, if we use scientific terminology.

At the tops of this cube is a carbon atom. One atom is located in each face, and four more - inside the cube. The central atoms in the faces are common to two cells, and those at the vertices of the cube are common to eight cells. The atoms are connected to each other by covalent sigma bonds.

This structure and packing is considered the most dense. Each carbon atom is located in the center of the tetrahedron and is connected on all sides. Since the valence of carbon is four, then all bonds are blocked, and interaction with the substance from the side is impossible.

The distance between the atoms is the same, there are no free electrons, so the mineral is a good dielectric. The hardness of diamond is achieved precisely because of this structure. These characteristics, in turn, led to the widespread use of stones. They are used not only in jewelry, but also as an abrasive, as well as a coating for tools.

But not everything in nature is perfect. Even diamonds often contain impurities. This structure allows the mineral to look absolutely transparent, without inclusions. But the mined stones do not always have jewelry properties due to a large number defects and impurities.

A diamond crystal may contain the following substances:

• aluminum;
• calcium;
• magnesium;
• granite.

Sometimes water, carbon dioxide or other gases are found in the composition. Impurities in the crystal are unevenly distributed and somewhat disturb the crystal structure. If defects are located on the periphery, which happens more often, then they can be dealt with by cutting.

Allotropic modifications

Not only diamond has a similar type of structure of the crystal lattice. Other elements from the fourth group also have a similar structure. But it's all about the atomic mass. Carbon atoms are located at a close distance from each other, which makes bonds stronger. But with an increase atomic mass elements are located further and the strength of the connections between them decreases.

And also carbon has allotropic modifications in nature, which, in addition to diamond, also include other substances:

• graphite;
• lonsdaleite;
• soot, coal;
• fullerenes;
• carbon nanotubes.

Scientists were interested in the possibility of turning graphite into diamond. This can be done only under the actions of very high pressure and temperature.

The thing is that graphite differs in the spatial arrangement of atoms and the bonds between them. If diamond has all covalent bonds - sigma, then the spatial bonds of graphite are pi compounds. And also in the graphite lattice there are a few free electrons at the atoms, which, moving, create the effect of electrical conductivity. This shape of the lattice is called hexagonal. Therefore, graphite has an indicator of unity on the hardness scale.

Lonsdaleites have not yet been fully studied, as they are mined either artificially or from meteorites that have fallen to the ground.

But fullerenes have a crystal lattice resembling a ball made of octagons. At the corners of the figures are not atoms, but molecules of carbon. These substances also continue to be investigated.

The chemical composition of diamond is written by the formula or element C.

In addition to the hardness index - 10 out of 10 on the Mohs scale - diamond has the following characteristics:

• Density - 3.5 g/cm3.
• The stone is quite fragile. Despite its hardness, a diamond can be shattered by a sharp blow.
• Cleavage. The density of the substance is uneven. The stone splits along the parallel faces of the crystal. Cleavage should be taken into account when cutting a stone, since the jeweler's calculation and subsequent blow determines the cleavage plane and cuts off unnecessary impurities.
• The stone must be transparent. Then after cutting it will play in the light. The most expensive specimens are called pure water diamonds. But still, up to 5% of impurities are found in the structure, which distorts the crystal lattice, and sometimes spoils the appearance of the stone.
• If the stone is exposed to x-rays, then the strength of covalent bonds will be broken. As a result, the lattice will become loose and the hardness of the substance will also decrease. But after this procedure, interesting property: The stone will emit light in the blue and green parts of the spectrum.

In nature, the mined mineral has the form of a crystal with a different number of faces. Sometimes not full stones are mined, but only chips from large diamonds. You can determine whether this is a chip or a full-fledged mineral by studying the structure of the crystal lattice. The faces of minerals are often covered with outgrowths and depressions.

The color of the diamond also varies. There are yellow, reddish or even black shades of diamonds. Of course, the crystal lattice of the stones has been changed. But the properties do not suffer much from this. Such minerals are called fantasy. Their color can be uneven and depend on impurities in the structure.

The ideal structure exists only in artificial diamonds. The production of these stones requires a seed in the form of a natural crystal, as well as a large amount of financial investment and equipment. But it was the study of the crystal lattice that influenced the development of this industry.