Allotropic substances: diamond and graphite. Formula of graphite and diamond. Polymorphic modifications of carbon: diamond and graphite Chemical properties of diamond and graphite table

12.03.2024 -

For an ordinary person, diamond and graphite are two completely different elements and in no way related to each other. Diamond evokes associations with iridescent jewelry; the expression “glitters like a diamond” comes to mind. Graphite is something gray, what pencil leads are usually made from.

It is hard to believe that both minerals are the same substance in different forms of processing.

Concept and main characteristics of minerals

Diamond is a transparent crystal that has no color and has high light refraction characteristics. The following main properties of the mineral are distinguished:

Nature generates both diamonds in certain shapes and in several crystalline forms, which is due to its internal structure. Pronounced crystals have the shape of a cube or tetrahedron with flat edges. Sometimes the edges appear raised due to the presence of numerous growths and transformations invisible to the eye.

Although many consider diamond to be the strongest material in the world, science knows a substance that is more than 11% stronger than diamond - “hyperdiamond.”

Graphite is a gray-black crystalline substance with a metallic luster. In composition, graphite has a layered structure; its crystals consist of small thin plates. This is a very brittle mineral, resembling steel or cast iron in appearance. Graphite has a low heat capacity but a high melting point. In addition, this mineral:

Graphite feels greasy to the touch and leaves marks when passed over paper. This occurs because the atoms of the crystal lattice are weakly bonded.

The difference between graphite and diamond, structural features and the process of transition of one mineral to another

Diamond and graphite are allotropic minerals with respect to each other, that is, they have different properties, but are different forms of carbon. Their main difference lies only in the chemical structure of the crystal lattice.

The crystal lattice of diamond has the form of a tetrahedron, in which each atom is surrounded by 4 more atoms and is the vertex of the neighboring tetrahedron, forming an infinite number of atoms with strong covalent bonds.

At the atomic level, graphite consists of layers of hexagons with atoms at the tops. Atoms are well connected to each other only at the layer level, but the layers do not have a strong connection with each other, which makes graphite soft and unstable to destruction. It is this feature that makes it possible to obtain diamond from graphite.

The physical and chemical properties of diamond and graphite are clearly visible from the table.

Characteristic
Structure of the atomic lattice	Cubic shape	Hexagonal
Light conductivity	Conducts light well	Does not allow light to pass through
Electrical conductivity	Does not have	Has good electrical conductivity
Atomic connections	Spatial	Planar
Structure	Hardness and brittleness	Layering
The maximum temperature at which a mineral remains unchanged	720 Celsius	3700 Celsius
Color	White, blue, black, yellow, colorless	Black, grey, steel
Density	3560 kg/m3	2230 kg/m3
Usage	Jewelry, industry	Foundry, electric coal industry.
Mohs hardness	10	1

The chemical formula of diamond and graphite is the same - carbon (C), but the process of creation in nature is different. Diamond occurs at very high pressures and instantaneous cooling, while graphite, on the contrary, occurs at low pressure and high temperature.

The following methods for obtaining diamonds are distinguished:

The diamond to graphite process is similar. The only difference is in pressure and temperature.

Mineral deposit

Diamonds occur at depths of more than 100 km at temperatures of 1300 °C. From the blast wave, kimberlite magma comes into action, forming so-called kimberlite pipes, which are the primary diamond deposits.

The kimberlite pipe is named after the African province of Kimberley, where it was first discovered. Rocks with diamond deposits are called kimberlites.

The most famous deposits today are located in India, South Africa and Russia. Up to 80% of all diamonds are mined from primary deposits consisting of kimberlite and lamproite pipes.

X-rays help find diamonds in mined rock. Most of the stones found are used in industry, as they do not have sufficient characteristics for jewelry. Industrial stones are divided into 3 types:

board - small stones with a granular structure;
ballas - round or pear-shaped stones;
Carbonado is a black stone that gets its name because of its resemblance to coal.

It is curious that the largest diamonds with outstanding characteristics receive their own unique name. The most famous of them are “Shah”, “Star of Minas”, “Kohinur”, “Star of the South”, “President Vargas”, “Minas Gerais”, “English Diamond of Dresden”, etc.

Graphite is formed as a result of the modification of sedimentary rocks. Mexican, Noginsk and Madagascar graphite deposits are rich in ore with low quality graphite. Less common are the Botogol and Ceylon types, characterized by ore rich in high graphite content. The largest known deposits are located in Ukraine and the Krasnodar region.

Scope of application

Diamond and graphite are used much more widely than it might seem at first glance. Diamonds have found their application in the following areas:

The percentage of diamond use looks like this:

Tools, machine parts – 60%.
Framing of grinding wheels -10%.
Wire recycling - 10%.
Well drilling – 10%.
Jewelry, small parts – 10%.

As for graphite, it is practically not used in its pure form, but is subject to pre-processing, although graphite of different qualities is used in different areas. The highest quality graphite is used for stationery pencils. It is most widely used in foundries, providing a smooth surface to various forms of steel. Almost unprocessed graphite is used here.

The electrocoal industry, along with natural graphite, uses artificially created graphite, which is also widely used due to its special purity and consistency of composition. Electrical conductivity has made graphite a material for electrodes in electrical devices. In metallurgy it is used as a lubricant.

Diamond and graphite are identical in composition, but unique in their own way. The benefits of graphite for various industries are much higher than diamond.

Diamond, designed to delight with its beauty, is invaluable to the economy, bringing huge profits from its use in the jewelry industry.

Introduction

1. Polymorphic modifications of carbon: diamond and graphite

1.1.General characteristics of diamond

1.2. General characteristics of graphite

2. Industrial types of granite and diamond deposits

3. Natural and technological types of diamond and graphite ores

4. Development of granite and diamond deposits

5. Applications of granite and diamond

Conclusion

Bibliography.

Introduction

The diamond industry of our country is at the stage of development, the introduction of new technologies for processing minerals.

Found diamond deposits are revealed only by erosion processes. For an explorer, this means that there are many “blind” deposits that do not reach the surface. Their presence can be recognized by the detected local magnetic anomalies, the upper edge of which is located at a depth of hundreds, and if you’re lucky, tens of meters. (A. Portnov).

Based on the above, I can judge the prospects for the development of the diamond industry. That is why I chose the topic - “Diamond and graphite: properties, origin and meaning.”

In my work, I tried to analyze the connection between graphite and diamond. To do this, I compared these substances from several points of view. I reviewed the general characteristics of these minerals, industrial types of their deposits, natural and technical types, development of deposits, areas of application, and the significance of these minerals.

Despite the fact that graphite and diamond are polar in their properties, they are polymorphic modifications of the same chemical element - carbon. Polymorphs, or polymorphs, are substances that have the same chemical composition but a different crystal structure. With the beginning of the synthesis of artificial diamonds, interest in the study and search for polymorphic modifications of carbon has sharply increased. At present, in addition to diamond and graphite, lonsdaleite and chaotite can be considered reliably established. The first in all cases was found only in close intergrowth with diamond and is therefore also called hexagonal diamond, and the second is found in the form of plates alternating with graphite, but located perpendicular to its plane.

1. Polymorphic modifications of carbon: diamond and graphite

The only mineral-forming element of diamond and graphite is carbon. Carbon (C) is a chemical element of group IV of the periodic system of chemical elements of D.I. Mendeleev, atomic number - 6, relative atomic mass - 12.011 (1). Carbon is stable in acids and alkalis and is oxidized only by potassium or sodium dichromate, ferric chloride or aluminum. Carbon has two stable isotopes C (99.89%) and C (0.11%). Data on the isotopic composition of carbon show that it comes from different origins: biogenic, non-biogenic and meteoritic. The variety of carbon compounds, explained by the ability of its atoms to combine with each other and the atoms of other elements in various ways, determines the special position of carbon among other elements.

1.1 General characteristics of diamond

The word “diamond” immediately brings to mind secret stories about treasure hunts. Once upon a time, people who hunted for diamonds had no idea that the object of their passion was crystalline carbon, which forms soot, soot and coal. This was first proven by Lavoisier. He experimented with burning diamonds using an incendiary machine assembled specifically for this purpose. It turned out that diamond burns in air at a temperature of about 850-1000*C, leaving no solid residue, like ordinary coal, and in a stream of pure oxygen it burns at a temperature of 720-800*C. When heated to 2000-3000*C without access to oxygen, it turns into graphite (this is explained by the fact that the homeopolar bonds between carbon atoms in diamond are very strong, which causes a very high melting point.

Diamond is a colorless, transparent crystalline substance that refracts light rays extremely strongly.

Carbon atoms in diamond are in a state of sp3 hybridization. In the excited state, the valence electrons in the carbon atoms are paired and four unpaired electrons are formed.

Each carbon atom in diamond is surrounded by four others, located away from it from the center at the vertices of the tetrahedron.

The distance between atoms in tetrahedra is 0.154 nm.

The strength of all connections is the same.

The entire crystal is a single three-dimensional frame.

At 20*C, the density of diamond is 3.1515 g/cm. This explains its exceptional hardness, which varies along the edges and decreases in the sequence: octahedron - rhombic dodecahedron - cube. At the same time, diamond has perfect cleavage (along the octahedron), and its bending and compressive strength is lower than that of other materials, so diamond is fragile, breaks apart when subjected to a sharp impact and, when crushed, turns into powder relatively easily. Diamond has maximum hardness. The combination of these two properties allows it to be used for abrasive and other tools operating under significant specific pressure.

The refractive index (2.42) and dispersion (0.063) of diamond far exceed those of other transparent minerals, which, combined with maximum hardness, determines its quality as a gemstone.

Impurities of nitrogen, oxygen, sodium, magnesium, aluminum, silicon, iron, copper and others are found in diamonds, usually in thousandths of a percent.

Diamond is extremely resistant to acids and alkalis, is not wetted by water, but has the ability to adhere to some fat mixtures.

Diamonds are found in nature both in the form of well-defined individual crystals and polycrystalline aggregates. Correctly formed crystals look like polyhedra with flat faces: octahedron, rhombic dodecahedron, cube, and combinations of these shapes. Very often there are numerous stages of growth and dissolution on the facets of diamonds; if they are not visible to the eye, the edges appear curved, spherical, in the shape of an octahedroid, hexahedroid, cuboid, and combinations thereof. The different shapes of crystals are due to their internal structure, the presence and nature of the distribution of defects, as well as physicochemical interaction with the environment surrounding the crystal.

Among the polycrystalline formations, ballas, carbonado and board stand out.

Ballas are spherulite formations with a radial structure. Carbonado - cryptocrystalline aggregates with the size of individual crystals 0.5-50 microns. The bead is clear-grained aggregates. Ballas and especially carbonado have the highest hardness of all diamond types.

Fig.1 Structure of the diamond crystal lattice.

Fig.2 Structure of the diamond crystal lattice.

1.2 General characteristics of graphite

Graphite is a gray-black crystalline substance with a metallic luster, greasy to the touch, and is inferior in hardness even to paper.

The structure of graphite is layered, inside the layer the atoms are connected by mixed ionic-covalent bonds, and between the layers by essentially metallic bonds.

Carbon atoms in graphite crystals are in sp2 hybridization. The angles between the bond directions are equal to 120*. The result is a grid consisting of regular hexagons.

When heated without air access, graphite does not undergo any change up to 3700 * C. At the specified temperature, it is expelled without melting.

Graphite crystals are usually thin plates.

Due to its low hardness and very perfect cleavage, graphite easily leaves a mark on paper that is greasy to the touch. These properties of graphite are due to weak bonds between atomic layers. The strength characteristics of these bonds are characterized by the low specific heat of graphite and its high melting point. Due to this, graphite has extremely high fire resistance. In addition, it conducts electricity and heat well, is resistant to many acids and other chemicals, easily mixes with other substances, has a low coefficient of friction, and high lubricity and covering ability. All this led to a unique combination of important properties in one mineral. Therefore, graphite is widely used in industry.

The carbon content in the mineral aggregate and the structure of graphite are the main features that determine quality. Graphite is often called a material that, as a rule, is not only monocrystalline, but also monomineral. They mainly mean aggregate forms of graphite substance, graphite and graphite-containing rocks and enrichment products. In addition to graphite, they always contain impurities (silicates, quartz, pyrite, etc.). The properties of such graphite materials depend not only on the content of graphite carbon, but also on the size, shape and mutual relationships of graphite crystals, i.e. on the textural and structural characteristics of the material used. Therefore, to assess the properties of graphite materials, it is necessary to take into account both the features of the crystalline structure of graphite and the textural and structural features of their other components.

Fig.3. Structure of the graphite crystal lattice.

Fig.4. Graphite phenocrysts in calcite.

2. Industrial types of diamond and graphite deposits

Diamond deposits are divided into alluvial and primary, among which there are types and subtypes that differ in terms of occurrence conditions, forms of ore bodies, concentrations, quality and reserves of diamonds, mining and enrichment conditions.

Primary kimberlite-type diamond deposits around the world are the main targets for exploitation. About 80% of natural diamonds are mined from them. Based on diamond reserves and sizes, they are divided into unique, large, medium and small. The upper horizons of unique and large deposits exposed to the surface are mined with the greatest profitability. They contain the main reserves and predicted diamond resources of individual diamond-bearing kimberlite fields. Kimberlites are “volcanic vents” filled with breccia. Breccia consists of fragments and xenoliths surrounding and deposited on top of rocks, from rock fragments carried from depths of 45-90 km or more. The cement is volcanic material, tuffs of alkaline-ultrobasic composition, the so-called kimberlites and lamproites. Kimberlite pipes are located on platforms, lamproite pipes are located in their folded frame. The time of formation of the pipes is different - from the Archean to the Cenozoic, and the age of diamonds, even the youngest of them, is about 2-3 billion years. The formation of pipes is associated with the breakthrough of alkaline-ultrobasic melts upward through narrow channels under high pressure, at a depth of over 80 km, at a temperature of about 1000*. Most well-studied kimberlite bodies have a complex structure; in the most simplified case, the structure of the pipe involves two main types of rocks formed during two successive phases of intrusion: breccia (1st stage) and massive “coarse porphyry” kimberlite (2nd stage). In the structure of some kimberlite pipes, kimberlite dikes and veins associated with the pipes were also identified. Blind bodies formed by portions of kimberlite magma that did not reach the surface were discovered. Deposits associated with dykes and kimberlite veins, as a rule, belong to the category of small, less often medium-sized diamond reserves. In many cases, the upward breakthrough reached the paleo-surface, but many explosion pipes may be “blind” and have not yet been exposed by erosion, t .e. lie somewhere deep. But there are also places on the surface of the Earth where pressures arise that are quite sufficient for the formation of diamonds. These are meteorite impact sites where diamond is found not only in the Earth, but also in a number of meteorites themselves.

The speed of movement of the erupting magma could probably be very high, about 800 km/h, the magma tore off and carried upward fragments of different compositions. If they contained diamonds, the pipe became diamondiferous. Diamonds themselves are the most stable polymorphic modification of carbon in the deep zones of the Earth. (A.V. Ukhanov.)

Rice. 5. Structure of a kimberlite pipe.

The lamproite type of diamond deposits was discovered relatively recently (1976) in Western Australia, where the large Argyle deposit is exploited. In terms of their structure, lamproite deposits are generally similar to kimberlite deposits. Judging by the exploration data of the Argyle deposit, lamproite pipes pinch out somewhat faster to a depth where they become dikes. The mining system for these deposits and the enrichment technology are the same as at kimberlite sites.

Kimberlite-lamproite type is represented by a diamond deposit in the Arkhangelsk region, where the content of indicator minerals is significantly lower than in “classical” kimberlites; the vast majority of diamonds are represented by curved forms.

Ring impact structures ranging in size from a few to hundreds of kilometers are associated with super-powerful explosive processes, the source of which, according to various researchers, was either extraterrestrial (fall of large celestial bodies) or endogenous. One deposit of this type has been explored in Russia - Popigaiskoye on the eastern slope of the Anabar crystalline massif. In terms of ore reserves and diamond content, the deposit is hundreds of times larger than the largest in kimberlites. However, diamonds in impact deposits are enclosed in strong, dense, effusive rocks and are represented exclusively by technical grades with an admixture of lonsdaleite (a polymorphic modification of carbon, found in the form of plates alternating with graphite, but located perpendicular to its plane).

The metamorphogenic type is also represented so far by one deposit on the territory of Kazakhstan, where diamonds are found in biotite gneisses, biotite-quartz, garnet-pyroxene and pyroxene-carbonate rocks. In terms of reserves and diamond content, it is tens of times greater than the largest highly diamond-bearing kimberlite pipes. Diamonds have extremely small crystal sizes, and jewelry and high-quality technical grades have not yet been discovered.

Placer diamond deposits are represented by five main types.

Alluvial placers (river valleys) are leading in terms of the scale of diamond mining from placers. Large deposits are rare and are usually formed due to the erosion of several primary sources or intermediate areal-type reservoirs. Alluvial placers have a two-member structure: the upper floodplain facies of alluvium is represented by very weakly diamond-bearing gravel-sand-clay and silt deposits (“peat”), the lower channel facies is composed of productive coarse-clastic pebbles (“sands”).

Placers of the deluvial-proluvial type are formed on slopes and in ravines near bedrock sources and are small and medium in scale.

Coastal marine placers are divided into underwater, beach and coastal terraces. The zone of such placers in southwestern Africa extends for many hundreds of km with a width of 5 to 20 km.

Placers of other industrial types do not play a significant role in diamond mining.

Placer deposits of various types according to their depth are divided into shallow and deep. According to the degree of remoteness from the root source, placers of near and distant demolition are distinguished; the former are formed close to the root source, the latter - at a distance of tens of kilometers in favorable geological and structural conditions.

Industrial types of graphite deposits.

Graphite was formed from organic compounds as a result of the metamorphization of sedimentary rocks.

Among graphite deposits, four groups of industrial types of deposits are distinguished based on the geological setting of their location.

Based on the size of reserves, graphite deposits are divided (million tons) into: large - more than 1, medium - 0.5-1, small - up to 0.5.

The most widespread and larger in terms of their reserves are deposits of the Taiga, Madagascar, Noginsk, and Mexican types.

Graphite deposits of the Ceylon and Botogol types are less common, less often have large reserves, but are distinguished by a high graphite content in the ore and more valuable qualities.

3. Natural and technological types of diamond ores

Natural types of ores are diamond-bearing kimberlites and diamond-bearing lamproites, which are divided based on the ratio of kimberlite proper and xenogenic material and structural and textural features into diamond-bearing massive kimberlites, kimberlite breccias, tuff breccias, xenotufo breccias, tuffs and tuffaceous-sedimentary rocks.

There is no unified technological classification of diamond ores. In the technical and economic typification of ores, two main technological types are distinguished: breccias with a clay component content of less than 20% and breccias with a clay component content of more than 20%. When processing these ores, both technological schemes and mining costs differ.

In general, as practice shows, the technological classification of ores is developed in each specific case independently during exploration and subsequent exploitation of the deposit. Often, when a kimberlite body is composed of rocks of different intrusion phases, clearly differing in structural and textural characteristics and level of diamond content, the natural types of ores practically coincide with the technological ones. The main factor is the diamond content. Thus, in the Dalnyaya pipe (Sakha-Yakutia), the two natural types identified here - kimberlite breccias and massive kimberlites - differ in the level of diamond content by an order of magnitude and are at the same time technological types. However, for example, during the operation of the Mir pipe, six technological types of ores were identified, differing in the nuances of structure and diamond content, while there were only two phases of introduction.

Technological types of diamond-bearing sands are distinguished based on their bouldering, clay content, permeability, etc.

Natural and technological types of graphite ores.

Typification of graphite ores is carried out according to textural and structural characteristics. Graphites are divided into clearly and cryptocrystalline. Among the clearly crystalline ones, densely crystalline and scaly varieties are distinguished. Densely crystalline graphites are divided into coarse-crystalline with an average crystal size of more than 50 microns and fine-crystalline.

According to the size of the flakes, their diameter, flake graphites are divided into large-flaky (100-500 microns) and fine-flaky (1-100 microns).

Cryptocrystalline graphites are composed of crystals less than 1 µm in size. Dense and finely dispersed or atomized varieties are distinguished. In the latter, graphite crystals are scattered in the host rock. In dense varieties, graphite crystals make up the bulk of the graphite rock. Only dense varieties of cryptocrystalline graphite are of industrial importance.

Crystalline lump – 92-95;

Crystalline coarse flake – 85-90;

Crystalline medium-flaky – 85-90;

Crystalline fine-flaky – 80-90;

Crystalline powders with a size of up to 0.074 mm and a graphitic carbon content of 80-99.

Exploration of graphite deposits of other industrial types, having deposits of irregular shape or lens-shaped and stock-shaped, is also carried out by core drilling wells in combination with mining workings.

When assessing and exploring graphite deposits using drilling, it is established that there is no selective abrasion of the core, which is possible with an uneven distribution of graphite concentrations, in the form of enriched areas represented by a network of veins, lenses, nests, etc. For this purpose, the graphite content in drilling fluids and cuttings should be monitored. If necessary, control workings are carried out with bulk testing.

4. Development of diamond deposits

Primary diamond deposits developed by open-pit or combined methods:

The upper horizons are open, and the deeper ones are underground. In Russia, diamonds are mined only by open-pit mining.

The open-pit method of developing pipes is approximately the same in all fields. Let's consider it using the example of the Fishy pipe (South Africa).

The pipe has an oval horizontal cross-section and almost vertical contacts with the host rocks. The weathering zone of kimberlites extends to a depth of 60 m. In the composition of kimberlites, a significant volume is occupied by the secondary phase - saponite, a swelling mineral that absorbs large amounts of water. For this reason, the pipe ore is hygroscopic and, when moistened, quickly loses its strength properties, so special methods are used to isolate the kimberlite surface from water, and when drilling wells, dry dust collection is used.

Open-pit development of the pipe began in 1966, and by 1990 the pit depth reached 423 m with an average annual decline of 18-20 m. Over 97 million tons of kimberlite were mined (about 5 million tons per year) and 55 million were disposed of in dumps. tons of waste rock. The surface area of the quarry is 550 thousand m2. This mining method ensured stable operation of the mine and good technical and economic indicators: low stripping ratio, systematic transition to the underground method. An inclined shaft with a length of 1300 m at an angle of 12° from the surface to the opening of the quarry at a depth of 280 m was driven through the host rocks. It housed a conveyor for transporting ore to the processing plant and an underground crushing complex, which made it possible to sharply reduce the number of operating dump trucks.

The underground method uses several systems for underground mining of diamond-bearing pipes.

The chamber system provides for the excavation of 8-meter chambers with a height of 12 m, separated from each other by temporary 8-meter pillars, at each working horizon along the short axis of the tube. Kimberlite, removed from the chambers and from the pillars of the overlying horizon, under the influence of the weight of collapsed rocks, falls on the base of the haulage mine, where it is loaded into trolleys and rolled back to the ore pass located in the host rocks, through which the kimberlite is fed to the main haulage horizon.

The slot mining method was used on the Premier pipe (South Africa). As the pipe was developed, at each working horizon, the main drifts ran parallel to the gap at intervals equal to half the distance from the gap to the boundaries of the ore body. At a depth of 270 m, ore was released from ore passes into trolleys and transported along haulage drifts. Next, the ore was fed into a crusher, crushed and transported to the surface. The most progressive development method is floor self-collapse; it provides high productivity (up to 5 million tons of kimberlite per year) at low cost and relatively little use of manual labor. With this system, kimberlite destruction occurs under the influence of gravity, the number of working horizons and loading points is sharply reduced. The essence of the system is that scraper drifts extend from the haulage drift, oriented across the tube, at a distance of 14 m from each other, in which square niches measuring 1-2 m are located at intervals of 3-5 m on both sides in a checkerboard pattern. the niches are occupied by the risers in the shape of a funnel, rising to a height of 7.6 m above the level of the base. The kimberlite blocks are then completely undercut and 18 m thick layers are mined so that the kimberlite breaks down and collapses into cone-like risers. As a result, a compensation gap 2.2 m high is formed over the entire area of the tube. After this, an unsupported kimberlite mass remains above the compensation space, which, under the influence of its own weight, gradually collapses onto the outlet funnels. As the kimberlite collapses, it is partially released in order to restore the compensation space, so the level of the collapsed kimberlite constantly rises until it reaches the rocks of the overlying horizon. After this, ore production continues at a certain rate until waste rock appears in the scrapers. Mining of this horizon ends here, after which they begin mining the underlying one.

Placer deposits with a depth of up to 40-45 m are processed using open-pit mining. In the Republic of Sakha (Yakutia), mining is carried out in the summer using bulldozer-hydraulic methods. The sands fed by bulldozers are washed on the grid of a hydraulic cradle with a cell size of 30-50 mm. The over-grid material is removed by a stream of water, and the under-grid pulp is transported through pipes by dredgers over a distance of 20.-2.5 km to a seasonal stationary processing plant. From the valley of extended placers, diamonds are mined by dredging. Dredges move from bottom to top along the river valley using transverse or longitudinal passages. After the main reserves are exhausted, the dredges are re-advanced from top to bottom with displacement of the strokes in relation to the primary ones. Sometimes the moves are directed across the primary ones.

Fig.6. Kimberlite pipe during development.

Development of graphite ore deposits.

The development of graphite ores is carried out by open and underground methods. Among the three exploited graphite deposits in Russia, two (Noginskoye, Botogolskoye) are developed underground and one (Taiginskoye) is developed open-pit.

The dimensions of the open pit mine at the Taiginskoe crystalline graphite deposit are about 3 km long, 200-250 m wide and more than 50 m deep. Mining losses are about 1%, dilution is insignificant.

In the USA, open-pit mining of graphite ore is carried out using drilling and blasting operations, followed by transportation of ore by road to processing plants.

An original system for developing graphite deposits was applied in the Republic of Madagascar. The open method processes mainly the upper, weathered graphite ores to a depth of 30-40 m. The work is carried out in terraces with the ore being lowered to the lower horizons, from where the ore is supplied to the processing plant.

The Noginsk graphite deposit, developed underground (adit and shaft), is characterized by dilution of 2.8%, ore moisture content of 4.5%, and losses of 17.8%.

The Botogol deposit of high-quality densely crystalline graphite is developed by the adit method. Mining is carried out in horizontal layers from bottom to top, with the filling of the treatment space. Production losses are about 8%.

5. Applications of diamonds

Main areas of application of natural diamonds.

Jewelry diamonds. The main area of application of diamonds in value terms is cutting into brilliants.

Industrial diamonds. Technical ones include dark-colored crystals that have cracks and other defects, as well as various fragments, doubles, intergrowths, etc., from which it is impossible to make a faceted crystal. Depending on the quality and purpose, industrial diamonds can be divided into the following groups:

Diamonds that are processed to produce grains of a specific geometric shape. These include diamonds intended for the manufacture of cutters, drills, tips, glass cutters, bearings, etc.;

Diamond crystals used in raw form in drill bits, diamond-metallic pencils, etc.;

Abrasive diamonds are basically small crystals that have significant defects and are only suitable for grinding into powder.

Diamond powders are indispensable when processing subminiature parts, such as ruby watch stones, bearings made of topaz, beryl and sapphire, the hardness of which approaches that of corundum. Only the use of diamond powders ensures high purity of the processed microsurfaces, which determines the accuracy of the microparts in devices and instruments.

Tools made from diamond powders. For cutting hard rocks, alloys and other hard materials, diamond blades and various diamond saws are produced by industry. Abrasive diamond tools in a mandrel are common and are widely used in the metalworking industry for dressing grinding wheels. Diamond metal pencils are also used, which are pressed inserts made of hard alloy diamond powder.

Tools made from single crystal diamonds. Cutters, needles, glass cutters, dies (plate-shaped diamonds with thin holes drilled into them) and other tools are made from individual diamond crystals or parts thereof. Diamond points are diamond crystals with a natural sharp point or sharp-edged shards set in metal rods. Diamond needles are widely used for making taps on thread grinding machines. Conical diamond needles with a spherical head are used in profilometers and profilographs, which are used to measure the smallest irregularities and surface cleanliness of various parts. Diamonds are widely used to make dies in the production of wire from hard materials, especially small diameters for electronics.

Diamond rock cutting tool. The use of diamonds to reinforce drill bits has made it possible to increase the productivity of drilling rigs by 1.5-2 times compared to non-diamond drilling.

Other areas of application of diamonds. Diamond is an excellent optical material for all kinds of cuvettes and windows, capable of withstanding high pressures and the impact of substances of any degree of aggressiveness and at the same time being transparent in a wide range of wavelengths.

The diamond substrate of semiconductor circuits, providing their excellent insulation, removes heat several times faster than, for example, copper, significantly increasing the operating efficiency of critical components of electronic circuits. The ability to use diamonds to count nuclear particles in aggressive environments and high mechanical loads; diamond is used in special counters.

The structure of consumption of industrial diamonds by highly developed countries is as follows, (%):

Grinding, sharpening of tools and machine parts made of hard alloys – 60-70;

Well drilling – 10;

Wire drawing – 10;

Cutting and grinding of parts and products made of glass, ceramics, marble, drilling and finishing of carbide parts, processing of watches and jewelry - 10-12.

Areas of application of graphite.

The ores of almost all graphite deposits can rarely be used by consumers in their raw form. Almost all of them undergo some kind of pre-processing in order to transform the ore into finished products.

The technological classification of graphite ores coincides with the classification of natural types.

Clearly crystalline ores are processed mainly using flotation schemes due to the good floatability of graphite.

Cryptocrystalline graphite raw materials are represented by finely dispersed minerals in a very complex intergrowth with waste rocks. Therefore, these types of graphite ores are almost impossible to mechanically enrich. They are mainly used for ore mining and, in special cases, chemical, thermal or other processing methods. Because these processes are expensive, it is rarely used.

The main indicators by which graphite products are assessed are: texture and structure, carbon content, ash, moisture, volatile components, harmful impurities (iron, sulfur, copper, etc.), particle size distribution.

In foundry production, preference is given to cryptocrystalline graphite, since the dispersion of the powder is important for this production, providing a smooth surface of the casting molds and facilitating the removal of castings from them after cooling.

High-quality clearly crystalline graphites are widely used in special steel casting.

Crucible graphite is available in three grades. Their zoning does not exceed 7; 8.5 and 10%, mass fraction of iron in terms of Fe2O3 for all grades is not more than 1.6%, volatile substances - less than 1.5%; moisture – no more than 1%.

For the production of graphite-ceramic melting crucibles and refractories, high-quality clearly crystalline graphite is used.

In accordance with the requirements for lubricating graphite, products are produced in the form of several grades, each of which has its own area of application and is characterized by a number of indicators. The only indicators common to all brands are the concentration of hydrogen ions in the water extract and humidity.

Pencil production, like electric carbon production, places the highest demands on the quality of graphite. In world practice, for the best types of pencils, a mixture of Ceylon and other crystalline or cryptocrystalline graphite is used, which is most often used for the production of ordinary types of pencils.

In the production of active masses of alkaline batteries, clearly crystalline coarse-flaked graphite (“silver”) is used, obtained by flotation of ores from the Taiginsky and Zavalevsky deposits.

In the electric coal industry, three types of graphite are used: natural fine- and cryptocrystalline and artificial. Artificial graphite has become widespread due to its high purity and consistency of composition.

In the production of lubricants, natural crystalline graphite and, together with it, artificial graphite are widely used as solid substances. This production requires graphite, usually of high purity and very fine grinding, sometimes of colloidal size. Lubricants are most often water or oil suspensions of natural crystalline and artificial graphite.

A number of graphite grades do not allow clogging impurities, including graphite from other deposits. These grades include crucible, elemental and electrocarbon graphite.

Conclusion

Having studied two polymorphic modifications of carbon: diamond and graphite, I came to the conclusion that despite the same chemical composition, the polymorphs have different crystal lattice structures, and therefore different properties and origins.

Diamond is a colorless, transparent crystalline substance with exceptional hardness – 10 and diamond luster. Graphite is a gray-black crystalline substance with a metallic luster, greasy to the touch, and is inferior in hardness even to paper - 1.

Diamonds occur in nature in the form of well-defined individual crystals. Graphite crystals are usually thin plates.

The origin of diamonds is igneous, graphite is metamorphic.

Diamonds are used in almost all industries: electrical engineering, radio electronics, instrument making, and drilling.

Graphite is used for the production of graphite-ceramic melting crucibles and refractories, as lubricants, in the production of pencils, and in the electric coal industry.

Countless textbooks show diamond-graphite equilibrium diagrams and say that diamond arises from graphite. But for some reason no one asked the question: where does graphite come from in the mantle?.. After all, it is unstable there, and it is called a “forbidden” mineral for mantle conditions. Carbides are a different matter. They are stable here: carbides of iron, phosphorus, silicon, nitrogen, hydrogen. Hydrogen carbide is a gas, ordinary methane, it is mobile and easily concentrated in deep fluid.

At one time, geologists did not attach importance to the remarkable discovery of the Soviet physicist B. Deryagin, who back in 1969 synthesized diamond from methane and, what is very important, at a pressure even below atmospheric. Even then, this discovery should have radically changed the existing ideas about diamond as a mineral that necessarily crystallizes from melts and at high pressures. B. Deryagin's data allowed me to consider the possibility of diamond crystallization from a fluid, a gas mixture in the C-H-O system.

It turns out that in such a fluid, oxygen at ultra-high mantle pressure loses its oxidizing properties and does not even oxidize hydrogen. But when gas rises upward, when a kimberlite pipe is formed, the pressure drops. It is enough to reduce the pressure 10 times - from 50 to 5 kilobars - for the activity of oxygen to increase a million times. And then it instantly combines with hydrogen and methane. Simply put, the gas spontaneously ignites - a furious fire breaks out in an underground pipe.

The consequences of such an underground “fire” depend on the ratio of carbon, hydrogen and oxygen in the fluid. If there is not too much oxygen, it will remove only hydrogen from the methane molecule (CH4). The resulting water vapor will be absorbed by mineral dust and form serpentinite, the most characteristic mineral of kimberlites. Carbon, remaining “lonely”, at a pressure of thousands of atmospheres and a temperature of about 1000 ° C, will close with unsaturated valence bonds “on itself” and form a giant molecule of pure carbon - a diamond! In practice, such a favorable combination of components in a gas mixture is rare: only five percent of kimberlite pipes are diamond-bearing.

More often it happens that there is either too much oxygen to form a diamond, or not enough. In the first case, carbon will burn and turn into gases - oxides: CO or CO2. Then barren kimberlites appear. They are characterized by increased magnetism because they contain iron oxide - magnetite. There was a lot of oxygen, and it “snatched” the iron from the silicates. If there is a deficiency of oxygen or methane, only water vapor will appear, and it will be absorbed by serpentinite. It turns out that diamond arises as a product of spontaneous underground combustion of carbonaceous fluid. Diamonds are analogues of ash or soot settled in the “chimneys” of the mantle! (A. Portnov – Doctor of Geological and Mineralogical Sciences, Professor).

Bibliography

1. Carbon and its compounds - Kyiv, “Naukova Dumka” 1978.

2. Bulakh A.G. General mineralogy. 1999.

3. Sarasovsky. Educational magazine. Volume 6, 2000. No. 5.

4. Dyadin Yu.A. Graphite and its inclusion compounds.

5. A. Portnov. “Diamond is soot from the underworld.”

6. JSC "Geoinformmarn". Moscow 1997. Mineral raw materials. Graphite. Diamond.

7. Publishing house "Soviet Encyclopedia". Moscow. 1972.

Hello, our dear readers! Have you ever wondered what diamond and graphite might have in common? It would seem that a diamond is what expensive jewelry is made from, pleasing the eye of even the most refined taste. Hard, tough and virtually indestructible. And graphite, the main element for making pencils, is very fragile and breaks easily. Remember how often your stylus broke?

However, both minerals are related to each other. Moreover, recreating special conditions makes it possible to carry out the process of transformation from graphite to diamond, and vice versa.

Reading the article will allow you to find out what properties the minerals presented in the article have, how they appeared on Earth in the first place, and where you need to go in order to mine diamonds. Or, if you’re less lucky, graphite, and also, is it possible to make diamonds and graphite at home?

We wish you pleasant reading!

Features of diamond and graphite

The main distinctive features of a diamond are:

the ability to refract and reflect sunlight, which gives it its famous shine;
the highest hardness (compared to other minerals) and fragility;
metastability – the ability not to change its structure and state for hundreds of years under normal conditions;
high thermal conductivity;
high resistance to acids and alkalis;
has a low coefficient of friction;
dielectric, does not conduct electric current.

Such properties of the mineral become possible due to the fact that its internal structure has a complex crystal lattice, which is a cube or tetrahedron. The structure is based on the chemical element carbon.

If there are impurities in its crystal lattice, it can change its color, which is familiar to everyone. Thus, the presence of iron in the composition gives the mineral a brown tint, lithium - yellow, aluminum - blue, manganese - pink or red (depending on the concentration), boron - blue, chromium - green.

Graphite is the exact opposite of diamond. Its structure consists of a number of layers that externally resemble thin plates. The main structural element is carbon. It has a black color with a hint of metal. Soft and slightly oily to the touch.

Has the following distinctive features:

does not transmit or refract light;
good thermal conductivity;
good fire resistance ability;
fragility;
low friction coefficient;
conducts electric current;
can be mixed with other substances.

Despite such different properties, modern science has learned to artificially produce the minerals presented here from each other.

Is diamond a mineral or not?

In order to answer this question, let’s figure out what a “mineral” actually is. In modern science, a mineral is considered to be a solid body of natural origin that has a crystalline structure, that is, the arrangement of atoms is strictly ordered.

Since the structure of diamond is a cube or tetrahedron and has a clear crystal lattice, it can confidently be classified as a mineral.

The situation is similar with graphite, the lamellar structure of which also has a strict order.

Origin of diamonds and graphite

There is no exact and reliable data on where these minerals came from. There are only some hypotheses, namely:

Hypothesis of igneous origin
Mantle origin hypothesis
Fluid origin hypothesis

The first two theories are the most popular and boil down to the fact that the appearance occurred in the depths of our Earth many millions of years ago at a depth of one hundred to two hundred kilometers. Crystals were brought to the surface as a result of explosions and volcanic eruptions.

Graphite, in turn, can also be formed as a result of changes in sedimentary rocks.

An interesting fact is the presence of diamond chips in meteorites. This suggests that in addition to terrestrial origin, there are also crystals of meteorite origin brought from space.

There are a number of hypotheses about how crumbs could form in meteorites. The most popular theory is that the meteorite itself does not contain diamond chips in a “pure” form, but is only enriched with carbon. Upon impact with the Earth, ideal conditions develop for the recreation of the mineral: high temperature (two to three thousand degrees) and pressure (from 5 to 10 GPa). Diamonds formed by this method are called impactites.

Unfortunately, crystals of cosmic origin are too small for industrial mining and therefore all deposits used for mining are only of natural origin.

Main deposits

The largest diamond deposits are located in the Indian Republic, Russian Federation, Kimberley Province (accounting for 80% of all production).

Russian deposits are located in the Republic of Sakha (Yakutia), Perm Territory and Arkhangelsk Region.

X-rays are used to detect diamond deposits. The search takes decades. A very small number of discovered deposits contain minerals of high quality, sufficient for use in the jewelry industry.

The mining process involves extracting the ore and crushing it, separating the associated rocks. After this, using special equipment, the categories and classes of the extracted material are determined.

The largest graphite deposits are located in the Krasnodar region and Ukraine. Deposits with low quality material are located in Madagascar, Brazil, Canada and Mexico.

As a rule, it is found together with limestone rocks, such as apatite and phlogopite, as well as in pneumatolite formations, namely: quartz, feldspar, biotite, titanomagnetite.

Application area

Used in many areas of industry.

electrical engineering;
radio electronics and power electronics;
drilling rigs;
production of precious jewelry and accessories.

Scope of graphite application:

creation of fire-resistant equipment;
production of lubricants;
production of pencil leads;
nuclear energy (as a neutron moderator);
artificial production of diamonds.

The most popular area of application is jewelry making. The processed mineral, called a diamond, has a high value and is very popular in the jewelry market. For many people, it is still an excellent investment option.

Technology for producing diamonds from graphite

For modern science, it is a mere trifle to grow an artificial diamond crystal. If under natural conditions it takes hundreds of millions of years to form, in a specially equipped laboratory this is carried out in much less time.

The principle of unnatural production is to recreate optimal conditions that are most favorable for changing the form of carbon. Both high temperature (from 1500 to 3000 degrees) and pressure (several GPa) are required. The easiest way to obtain it is to pulse heat graphite to two thousand degrees. By maintaining high pressure, the process of converting graphite into diamonds takes place. At the same time, when the pressure decreases, the reverse process starts, in which one mineral turns into another.

In this regard, to obtain a diamond crystal, it is necessary to stably maintain high temperature and pressure parameters for a long time. This makes the conversion technology energy-intensive and costly. In addition, this process produces only industrial diamond, which is unsuitable for use in jewelry.

For these reasons, unnatural diamond production is considered unprofitable compared to mining.

Preparation of artificial graphite

There are the following types of artificial graphites: blast furnace, coke, retort, Acheson.

The most popular unnatural type is coke. The production method involves obtaining a dense carbon mass from sand and coke, firing it, associated with carbonization. At the last stage, crystallization (graphitization) occurs. To reduce porosity, the resulting mineral is impregnated with synthetic resins and roasting is repeated. Each repeated cycle significantly reduces porosity. There can be up to five cycles in total.

A significant disadvantage of artificial graphite is the content of various impurities and, accordingly, low “purity”.

That's all! Thank you very much for your interest and attention! Don't forget to recommend this article to your friends on social networks!

Team LyubiKamni

Hard diamond that plays in the light and opaque, easily peeled graphite can be figuratively called siblings. After all, the chemical composition of both contains only one element – carbon. Let's find out why, having a common origin, these minerals are so different from each other and how diamond differs from graphite.

Definition

Diamond- a mineral based on carbon. It is characterized by metastability, that is, the ability to exist in an unchanged form under normal conditions for an indefinitely long time. Placing diamond in specific conditions, for example in a vacuum at an elevated temperature, leads to its transition to graphite.

Diamond

Graphite– a mineral that acts as a modification of carbon. During friction, scales are separated from the total mass of the substance. The most famous use of graphite is making pencil leads from it.

Graphite

Comparison

The phenomenon in which substances have different properties, but are formed by a common chemical element, is called allotropy. However, in nature, perhaps, there are no longer such completely different allotropic forms of the same element. What explains the difference between diamond and graphite?

The decisive role here is played by the characteristics of the crystal structure of each substance. Let's talk about diamond. The bond between its atoms is incredibly strong. This is due to the way they are located relative to each other. Adjacent atomic cells of a substance have a cubic shape. Particles are located in the corners of cells, on their edges and inside them. This type of structure is called tetrahedral.

Diamond cell

This geometry of atoms ensures their most dense organization, due to which the diamond becomes hard and resistant to deformation. At the same time, it is a fragile substance that can crack under impact. The structure also determines the high thermal conductivity of diamond and the ability of its crystals to refract light.

Graphite has a different structure. At the atomic level, it consists of layers located in different planes. Each layer is made up of hexagons adjacent to each other, like a honeycomb. The bond between the atoms that are the vertices of the hexagons is strong only within each layer. And atoms located in different layers are practically independent of each other.

Graphite structure

Pencil marks are easily removable layers of graphite. Due to its structural features, the substance absorbs light, taking on a rather inconspicuous appearance (but with a metallic sheen), and is electrically conductive.

The inherent properties of minerals determine their suitability in a particular area. What is the difference between diamond and graphite regarding their applications? A brilliant diamond is ideal for jewelry production. And the hardness of this material allows it to be used to make high-quality glass cutters, super-strong drills and other popular products.

Graphite rods play the role of electrodes during many processes. Crushed graphite is part of mineral paints and is used as a lubricant. And from a mixture of this substance and clay, special containers for melting metals are produced.

Introduction

1.1.General characteristics of diamond

1.2. General characteristics of graphite

2. Industrial types of granite and diamond deposits

3. Natural and technological types of diamond and graphite ores

4. Development of granite and diamond deposits

5. Applications of granite and diamond

Conclusion

Bibliography.

Introduction

The diamond industry of our country is at the stage of development, the introduction of new technologies for processing minerals.

Based on the above, I can judge the prospects for the development of the diamond industry. That is why I chose the topic - “Diamond and graphite: properties, origin and meaning.”

1. Polymorphic modifications of carbon: diamond and graphite

1.1 General characteristics of diamond

Diamond is a colorless, transparent crystalline substance that refracts light rays extremely strongly.

Carbon atoms in diamond are in a state of sp3 hybridization. In the excited state, the valence electrons in the carbon atoms are paired and four unpaired electrons are formed.

Each carbon atom in diamond is surrounded by four others, located away from it from the center at the vertices of the tetrahedron.

The distance between atoms in tetrahedra is 0.154 nm.

The strength of all connections is the same.

The entire crystal is a single three-dimensional frame.

The refractive index (2.42) and dispersion (0.063) of diamond far exceed those of other transparent minerals, which, combined with maximum hardness, determines its quality as a gemstone.

Impurities of nitrogen, oxygen, sodium, magnesium, aluminum, silicon, iron, copper and others are found in diamonds, usually in thousandths of a percent.

Diamond is extremely resistant to acids and alkalis, is not wetted by water, but has the ability to adhere to some fat mixtures.

Among the polycrystalline formations, ballas, carbonado and board stand out.

Fig.1 Structure of the diamond crystal lattice.

Fig.2 Structure of the diamond crystal lattice.

1.2 General characteristics of graphite

Graphite is a gray-black crystalline substance with a metallic luster, greasy to the touch, and is inferior in hardness even to paper.

The structure of graphite is layered, inside the layer the atoms are connected by mixed ionic-covalent bonds, and between the layers by essentially metallic bonds.

Carbon atoms in graphite crystals are in sp2 hybridization. The angles between the bond directions are equal to 120*. The result is a grid consisting of regular hexagons.

When heated without air access, graphite does not undergo any change up to 3700 * C. At the specified temperature, it is expelled without melting.

Graphite crystals are usually thin plates.

Fig.3. Structure of the graphite crystal lattice.

Fig.4. Graphite phenocrysts in calcite.

2. Industrial types of diamond and graphite deposits

Allotropic substances: diamond and graphite. Formula of graphite and diamond. Polymorphic modifications of carbon: diamond and graphite Chemical properties of diamond and graphite table

Concept and main characteristics of minerals

The difference between graphite and diamond, structural features and the process of transition of one mineral to another

Mineral deposit

Scope of application

Features of diamond and graphite

Is diamond a mineral or not?

Origin of diamonds and graphite

Main deposits

Application area

Technology for producing diamonds from graphite

Preparation of artificial graphite

Definition

Comparison

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