Mel is educated. Research work "Composition of chalk

Who among us does not know what chalk is? It can be called a "witness of epochs" that passed tens of millions of years ago. This compound is of biological origin, therefore it has numerous chemical and physical properties.

Features of origin

Arguing over what chalk is, let's pay attention to its appearance in nature. About 80 million years ago, when dinosaurs existed on Earth, there was the Cretaceous period. In the small seas of that time, millions of small mollusks lived, which built their shells and skeletons from the calcium contained in the water. The remains of creatures accumulated in layers of many meters in bottom sediments and turned into white chalk.

The composition of the mineral

In percentage terms, several components of this mineral can be distinguished:

about 10% are fragments of the skeletons of the simplest creatures, multicellular animals that can accumulate calcium in tissues;
up to 10% of chalk is part of the shell of small foraminifera mollusks;
fragments of algae growths contain up to 40% calcium salts. A living microscopic suspension in the seas is coccolithophores, which create lime silt;
up to 50% is crystalline finely dispersed calcite;
lumpy chalk (in the form of silicates) - up to 3%. It is presented in the form of geological debris (sand, rock remnants), which are carried by winds and currents into the Cretaceous deposits.

Composition

Arguing over what chalk is, consider its composition. In chemistry, this name was given to calcium carbonate, which is a salt of carbonic acid. Let's take a closer look at its composition. White chalk contains up to 50% calcium oxide, and about 2% magnesium oxide. What substances give color to this mineral? Studying what chalk is, we note that in some cases, it may contain even 3-4% aluminum oxide, as well as minimal amounts of iron oxides. How does this affect the appearance of the mineral? In this case, the drawing chalk acquires a red or pink tint.

Can blackboard chalk be eaten? In case of a lack of calcium in the body, a person develops a craving for eating chalk. Doctors are ambivalent about this issue. When chalk is exposed to gastric juice (concentrated hydrochloric acid), it significantly changes its properties.

Chalk, having gone through many oxidative processes, loses its original neutrality, turns into an aggressive chemical compound, similar in properties to slaked lime (calcium hydroxide).

That is why, upon contact with oxidized chalk, the mucous membrane of the digestive organs is seriously affected.

If you eat chalk for a board in large quantities, this provokes liming of the vessels. Much safer with a lack of calcium is the use of special medications, such as calcium gluconate.

Doctors warn patients about the inadmissibility of using agricultural fodder, construction, stationery chalk for food.

Areas of use

It is not advisable to use chalk as a masonry material, since it has a slight hardness. How is this mineral mined? Basically, school chalk is obtained by open pit mining. The mined blocks are crushed, then lowered into the water.

With constant stirring, floating to the surface of calcium particles is observed. They are dried and used for various purposes. Stones that have not undergone such processing are sent for firing, as a result of which lime is formed.

Construction chalk

It has long been used for whitewashing indoor ceilings. Currently, such a scope is practically absent, since other finishing materials have appeared.

Currently, chalk is introduced into the composition of cement mixtures to give them additional softness.

Also, the mineral is in demand in the manufacture of glass, rubber, plastics, paints and varnishes, composite mixtures, rubber.

Chalk is used in large quantities in the linoleum and carpet industries. With its help, I regulate the viscous properties of latex glue, give products strength, and improve heat-saving characteristics.

The calcium mineral is also necessary for the production of soil fertilizers and animal feed. Chalk powder is the basis for the creation of numerous cosmetic products: powder, creams, lipstick. It is difficult to imagine the functioning of the cardboard and paper industry without chalk.

Chemical-physical characteristics

Depending on the characteristics of the deposit, there may be significant differences in the natural characteristics of chalk. Humidity has a significant effect on the material. Chalk does not dissolve in water, it forms a suspension. When moisture is absorbed, calcium carbonate loses its strength, while the plasticity of the material increases significantly. This introduces serious problems in the extraction and processing of the mineral, it sticks to the excavator bucket. Chalk has low frost resistance. After thawing, the material breaks up into many separate small particles. This quality is used in agriculture to reduce the acidity of the soil.

Differences between lime and chalk

Despite the common roots, these materials differ in properties and composition. Both are considered environmentally friendly, but chalk contains carbon dioxide, and lime is obtained by firing natural limestone.

In order to independently distinguish between chalk and lime, you can take a small handful of each material, grind to a dusty appearance, then rinse with a small stream of water. Chalk will immediately be removed along with water, but in order to get rid of lime, you will have to work hard.

There are no traces of lime whitewash, but the chalk will remind of itself for a long time even after the repair is completed. Lime has excellent antiseptic characteristics, so it is used to protect trees and shrubs from insect infestation.

Finally

Chalk is a material that is familiar not only as a tool of work for teachers in schools, but also as a historical witness to the events that took place on our planet millions of years ago.

Its main part is made up of calcium deposits of the shells of the simplest prehistoric plants and microorganisms.

Cretaceous deposits are currently needed in various areas of production: in the creation of paints, the manufacture of cosmetics, the development of food additives. Cretaceous natural deposits often include various undesirable impurities: sand, stones, various mineral particles.

That is why the chalk mined in the deposits is first crushed, then mixed with water, getting a suspension. Heavy impurities settle to the bottom, light chalk particles are caught in a special container. After adding an adhesive composition to them, drying, chalk is obtained, suitable for drawing on a school board.

Among the new uses of chalk, one can single out its application on the playing field. Fine particles of this substance rise into the air, so the players can clearly see the lines made.

To remove sweat, fat, chalk powder is also in demand in some sports: weightlifting, gymnastics, rock climbing.

The finished product is an excellent component of toothpastes and powders. It is used as a filler in the manufacture of cardboard and paper products.

The raw quarried mineral is needed in the construction industry for the production of lime.

Chalk is used in various fields - from industry to medicine. But for some people, this is food that they gnaw with pleasure. Someone starts from the school bench, and someone at a conscious age.

“As a child, I picked whitewashed walls at home, then I carried chalk at school - it was the most delicious there. Not what it is now - pressed, with lime, - the Belgorod woman shared Ninel. - Now I take chalk in my own store: I deal with seeds and all sorts of other things for the garden and vegetable garden. This construction chalk is like a powder. It happens that I eat three spoons of it every day. And I can't explain why I want it. They say this happens when the body lacks calcium.

There are huge deposits of chalk in the Belgorod region - the names of settlements also speak of this: Belgorod, Belomestnoye, Melovoe. Kreid is completely translated from Ukrainian as "chalk". Soft white limestone is found mainly in the southeastern, southern and southwestern regions.

Belgorod chalk is being ordered with might and main through online stores. For example, on Amazon, 200 grams of limestone is sold for $15. Anastasia from Belgorod and earns on chalk, and eats it herself:

“When my husband and I come to the mountain, I look where the chalk is better. We cut off a suitable piece and immediately pack it, and when we arrive home, we process it: we bake it in the oven or dry it in the air.”

white business

Nastya started selling recently. At first I read forums on the Internet, and then I decided.

She sells 100 g of chalk for 50 rubles, however, people take several kg at once. According to the girl, there are about 100 people in her customer base.

“I have clients who have been eating chalk for 30 years since high school. I joined this hobby not so long ago: three years ago. Chalk contains calcium, which is very useful for our body, because it is the basis of the bone structure. In addition, chalk normalizes the iron content in the blood and has a very good effect on tooth enamel, preventing the occurrence of caries. And he also helps people suffering from heartburn, ”says Anastasia.

Photo by Vadim Zablotsky

Russian-speaking chalk sellers don't bother with names. The packages are named by origin: Sevryukovsky, Novooskolsky, Orenburg, Volokonovsky, Belgorod, Chernigov, Artyomovsky, Kramatorsk and others. According to connoisseurs, the taste of chalk depends on where it was mined. There are even videos on the Internet with recipes on how and what types of chalk are best mixed in a plate and how to bake chalk cakes.

“There is soft creamy chalk that immediately dissolves in the mouth, turning into gruel, has the smell of concrete and plaster,” Nastya explained. - There is hard chalk with the smell of rain, which is hard to bite off, and when chewed it turns into a grain. There is chalk interspersed with clay - for gourmets. That's what it's called - clayey."

Ours is tastier

Melodists write on their forums that sawn chalk from Belgorod differs from Orenburg in structure, color and hardness: it is softer and melts in the mouth. And in general, it is famous for being more popular with small things than any other.

On the YouTube about 6 thousand videos, where people of different ages taste chalk from the Belgorod region on camera, covering their faces. An unusual delicacy is becoming more and more popular every day not only among Russians, but among Americans, Europeans and Asians.

By the way, meloids are ashamed to talk about their passion. Of the 30 interviewees found on the chalk forums, only two answered us.

“I don’t understand why it should be embarrassing to eat chalk if that’s what nature gives us. People began to eat chalk since ancient times, when there were no toothpastes, shampoo, medicines. Our ancestors used chalk for these purposes and added it to food. That is why our grandparents are so strong and hardy,” says Anastasia.

On different sites where they sell chalk, they write almost the same thing: “ Only pure natural chalk mined in the quarries of the Belgorod region! Lump chalk is not subjected to any chemical treatments, unlike industrial and clerical!»

However, what is interesting is that food chalk is not produced in Belgorod, the maximum is for animal feed. There is no food GOST for it - in principle it does not exist in Russia. And there is no certification for products on the Internet. Therefore, one can only guess what additives sellers use in their product.

Legal income?

From a legal point of view, such earnings cannot be called legal.

“Land and other natural resources are in private, state, municipal and other forms of ownership. Chalk is the same resource, - explained the representative of the company "Jurist Karamazov" Alexey Kolesnikov. - And here it is important to know who owns the chalk quarry. If privately owned, then such extraction of chalk will be theft: if chalk was collected for more than 2 thousand rubles, this is criminal liability under Art. 158 of the Criminal Code of the Russian Federation, if less - under Art. 7.27 of the Code of Administrative Offenses.

Most often, chalk quarries are in use by the state, and only individuals are allowed to mine chalk and other natural resources. This is regulated by Art. 11 of the Law of the Russian Federation "On Subsoil". In particular, the law states that use is formalized by a license. And if chalk is mined without it, they will be held accountable. According to Art. 7.3 of the Code of Administrative Offenses of the Russian Federation for violation of the rules for the use of subsoil, you can pay a fine of 3 thousand to 5 thousand rubles, for officials - from 800 thousand - up to 1 million.

In addition, citizens who sell goods and are neither individual entrepreneurs nor legal entities may be held liable for illegal activities and non-payment of income taxes.

Dangerous infatuation

Head of the Center for Public Health and Family Prevention Ludmila Kropanina warns that calcium abuse can lead to severe disorders, the formation of stones in the body and major kidney problems:

“Calcium is absorbed only when it enters the body with additional contributing substances, and the calcium that we have in quarries is not optimal for absorption. The risk of metabolic disorders will be 100%.
This topic with chalk did not appear just now - it has always been relevant. Just before chalk lovers could not gather in one place due to the lack of the Internet. People who have a need for the use of chalk should consult a doctor. They probably have something unbalanced: thyroid gland, high stress, overweight or something else. The hype that is observed with melodies is the lack of information and the lack of medical influence. These users need a different therapy - and it's not chalk."

Alena Antonova

Chalk is a natural material of organic origin, a rock from the sedimentary category. If you figure out what chalk consists of, then the basis of the mineral is deposits formed many millions of years ago from fragments of animal skeletons, mollusk shells, and calcareous growths of algae. About 50 percent of the mass is made up of fine particles of crystalline calcite, the origin of which has not been established.

In chemical terms, it is officially considered that the formula of chalk is calcium carbonate CaCO3. However, in reality, the composition of chalk looks a little different:

about half of the mineral is calcium oxide CaO (47-55%);
about 43% is carbon dioxide CO2;
2% by weight is magnesium oxide MgO;
up to 4% in the composition of chalk is aluminum oxide Al2O3.

In addition to the above, chalk necessarily contains quartz inclusions in very small quantities. Some deposits give out a mineral with a reddish tint, which means that iron oxides are present in its composition.

Areas of use of chalk

It is impractical to use chalk as a masonry material due to its extremely low hardness. However, the premises carved into the massifs of Cretaceous deposits have been preserved for centuries in their original form and are quite suitable for life.

How is chalk mined? Most often, these are open pit developments. The resulting lumps are crushed and placed in water. When stirred, particles of calcium float. Subsequently, they are dried and used for various purposes. Unprocessed stones are sent for firing to obtain lime.

Chalk is called construction chalk, which was previously used for whitewashing the interior surfaces of rooms. Now this scope of its application has come to naught, as many other, more advanced finishing materials have appeared. Where is chalk used?

The mineral is included in the composition of cement mixtures when it is necessary to give them softness.
In the production of glass, paints and varnishes, rubber, plastics, rubber, in the creation of composite materials based on PVC.
Chalk is actively used in the carpet and linoleum industry. It helps to regulate the viscous properties of latex adhesives, give products strength and improve heat-saving properties.
Chalk has found application in the manufacture of animal feed and soil fertilizers.
Chalk powder is the basis for most cosmetics - lipstick, creams, powder.
The paper and cardboard industry cannot do without chalk.

Is chalk harmful? It is absolutely safe, and the best proof of this is its use in the creation of toothpastes and powders. Moreover, the lack of calcium in the human body causes a desire to eat a piece of chalk. In this case, you should not use whitewash chalk or school crayons. Pharmacies have special drugs, such as calcium gluconate.

Physical and chemical indicators of chalk

The natural characteristics of chalk from different deposits can vary significantly. Moreover, the properties of the mineral can be different even at different horizons of the same quarry. This is due to certain conditions of its formation and the degree of humidity. Therefore, the physicochemical properties of chalk, given in the following table, are indicative.

No. p / p	Name of indicator	Unit measurements	Indicator
	Appearance		White powder
	Mass fraction of CaCO3 + MgCO3 in terms of CaCO3
	Mass fraction of iron and aluminum sesquioxides
	Mass fraction of substances insoluble in hydrochloric acid
	Mass fraction of water-soluble substances
	Mass fraction of iron oxide
	Chalk density, in pieces
	The same, bulk
	Humidity
	Modulus of elasticity in loose state
	The same, in dense form
	Temporary compression strength

Humidity has a great influence on the material. Does chalk dissolve in water or not? When powder is mixed with water, a suspension is obtained, but not a solution. But the presence of water significantly changes the physical properties of the material. In particular, strength indicators decrease, but plasticity appears. Often this complicates the process of extraction and processing. The material sticks to the excavator bucket, car body, conveyor belt. Excessive moisture makes it impossible to extract rock from the lower horizons.

Frost resistance in chalk is extremely low. After defrosting, it breaks up into small particles. However, this quality is useful for deoxidizing the soil, where chalk is used. Pieces of chalk rock up to 100 mm in size are introduced into the soil, which, when plowing and overwintering, are themselves destroyed, and their neutralizing effect lasts for a long time.

How not to confuse chalk with lime

What is the difference between chalk and lime? Although the materials have common roots, they are completely different both in composition and in properties. Chalk contains carbon dioxide, which is not present in lime. Both are environmentally friendly. But chalk is simply mined in quarries, and lime is obtained by firing natural limestone.

How to distinguish chalk from lime on your own? You can use primitive methods. Materials have a different reaction to the action of any acid. It is enough to drop vinegar or lemon juice on the test piece of material. Chalk will hiss, and the interaction of lime with acid will not be accompanied by any sounds.

One more way. You need to take a pinch of material, grind it and try to wash it off with a thin stream of water. Chalk will leave with water immediately and without a trace, and lime is washed off for a long time, leaving the impression of fat.

The mixing of quicklime with water is accompanied by a strong reaction with the appearance of foam. Chalk just gets wet. Lime whitewash does not leave marks if you run your hand over it, unlike chalk. In addition, lime has antiseptic properties, it is a good protection, in particular trees, from fungal infections and insects.

Chalk is a sedimentary rock of organic origin. The structure of the material is fine-grained, crumbly and soft, weakly cemented. Natural chalk is white. It does not dissolve in water. The mineral composition resembles limestone.

Chalk includes:

skeletal fragments;
foraminifera shells;
seaweed fragments;
fine calcite;
insoluble minerals.

A careful analysis of the Cretaceous sediments reveals impurities in the form of very small grains of quartz. Cretaceous deposits may contain fossils dating back to the Cretaceous period: ammonites and belemnites. Natural chalk is not characterized by layering and recrystallization. Numerous burrows of soil-eating animals are included in the structure of the material.

Calcite, which dominates in the complex composition of chalk, can be of both autogenic and biogenic origin. Up to 75% of the rock is composed of organic remains. In their bulk, they are represented by skeletons and shells of plankton and foraminifers. Skeletal remains in the chalk are very small - only 5-10 microns. This substance may also contain the skeletons of bryozoans, shells of mollusks, the remains of sea urchins, corals, flint sponges.

Up to 10% of the volume of chalk are impurities of the non-carbonate type:

kaolinite;
glauconite;
feldspars;
quartz;
pyrite;
opal;
chalcedony.

Flint and phosphorite are much less common.

Cretaceous strata often cross large cracks filled with chalk flour. The network of such cracks usually thickens closer to the surface. At different levels of horizontal layers, chalk differs in its mechanical properties and chemical composition.

According to the structural properties and physical characteristics, three types of chalk are distinguished:

white writing;
marly;
chalky limestone.

Chalk chemical properties

The chemical composition of chalk is determined by the high content of calcium carbonate with inclusions of magnesium carbonate. The chalk may also contain a non-carbonate part, including metal oxides. It is generally accepted that the chemical formula of this substance corresponds to the well-known formula of calcium carbonate (CaCO3). But the real composition of chalk is more complicated. This mineral contains about half of calcium oxide. Up to 43% of the chalk composition is carbon dioxide; it is in a bound state. Approximately 2% of the total mass of the substance is magnesium oxide. Mandatory, although not too significant, inclusions of quartz. Chalk with a relatively high silicon content has a higher density. Chalk contains a small amount of aluminum oxide, and iron oxides quite often color chalk layers red.

The carbonate part of the chalk is soluble in hydrochloric and acetic acids. The non-carbonate part includes quartz sand, clays, and metal oxides. Some of these components do not dissolve in acids. In small quantities, the chalk includes particles of magnesian calcite, as well as dolomite and siderite.

The molecular formula of chalk corresponds to several types of crystalline compounds that contain ions in the lattice sites.

Physical properties of chalk

Chalk is considered a semi-rock of a hard type. The strength of this mineral is determined by moisture. When water is exposed to chalk, the strength characteristics of chalk decrease. Changes often occur already at 2% humidity. At 35% humidity, the compressive strength increases by about 2-3 times, the chalk becomes plastic. This physical property makes it difficult to process the substance. Chalk begins to actively stick to the working parts of the machines. The viscosity and plasticity of chalk often do not allow it to be extracted from the lower horizons.

The density of chalk reaches 2700 kg/cu. m; porosity - up to 50%. Humidity in natural environment ranges from 19 to 33%. If the chalk is moistened, its strength is markedly reduced. At a moisture content of about 30%, chalk exhibits its plastic properties. Chalk found in nature is not resistant to frost. After multiple cycles of freezing and thawing, the chalk usually breaks into small pieces.

When analyzing the physical properties of chalk, special attention is paid to the behavior of the rock during grinding. In the technological process, it is customary to set the rate of chalk blooming in a humid environment with controlled mechanical action. The modulus of elasticity of chalk for a loose state is 3000 MPa, for compacted - 10000 MPa. Temporary compressive strength: 1000-4500 MPa.

Calcium carbonate, being in a crushed form, has a high dispersion. The presence of chalk in the product reduces its abrasiveness. The physical properties of this substance help to increase the thermal resistance of products, their mechanical strength, resistance to weathering and exposure to reagents.

Previously, it was believed that the chemical and physical properties of chalk are the same for all deposits. However, practice has shown that this is not the case. The properties of Cretaceous deposits differ even within the same deposit. Therefore, when mining a mineral by industrial means, technological mapping is performed. The chemical properties of chalk and its physical characteristics are studied in different areas of the deposits. Places of accumulation of high-quality chalk rocks are put on the maps.

Chalk deposits

The richest deposits of chalk are located in Europe. It can be found from Western Kazakhstan to the British Isles. The thickness of the chalk layers reaches hundreds of meters. In the Kharkov region, deposits with a thickness of up to 600 m were discovered. A huge chalk belt stretches across Europe, capturing the northern part of France, the south of England, Poland, Ukraine, and Russia. Part of the deposits is displaced to Asia; chalk reserves are found in the Libyan desert and in Syria.

In the United States, chalk deposits have been noted only in the southern and central states. However, the chalk there is of poor quality; for this reason it has to be imported into the US from Denmark, the UK and France.

Chalk reserves are distributed very unevenly. Up to half of high-quality chalk with a good content of calcium carbonate is concentrated in the Russian Federation. In absolute terms, chalk reserves in Russia are estimated at 3,300 million tons. Unlimited forecast chalk deposits are located in the Belgorod region. Very high quality chalk with a low content of non-carbonate impurities is mined in the Voronezh region.

The practical value of chalk

The practical use of chalk is determined by its chemical and physical properties. In industry, it is used for the production of cement, lime, soda, glass and school crayons. Chalk also serves as a filler for plastics, paper, rubber, paints and varnishes. It is included in the formulation of toothpastes and powders.

Chalk also finds application in agriculture: it is used for liming the soil and as a top dressing for animals, to protect tree trunks from sunburn.

Chalk is a necessary component in the production of coated paper. It is widely used in the printing industry for the manufacture of illustrated publications. Chalk is successfully used as the main filler and pigment in the manufacture of cardboard.

Chalk also finds application in construction. Cheap ground chalk is used for whitewashing, priming, wall painting.

Chalk is a carbonate sedimentary rock of white color, fine-grained, weakly cemented, soft and crumbly, insoluble in water, of organic (zoogenic) origin. In terms of mineral composition, chalk is close to limestone and is composed mainly of calcite (91-98.5%). The basis of the chemical composition of chalk is calcium carbonate with a small amount of magnesium carbonate, but there is usually a non-carbonate part, mainly metal oxides. In the chalk, there is usually an insignificant admixture of the smallest grains of quartz and microscopic pseudomorphs of calcite after fossil marine organisms (radiolaria, etc.). Often there are large fossils of the Cretaceous period: belemnites, ammonites, etc. Natural chalk is characterized by the absence of recrystallization and layering, a large number of passages of various worm-eating animals (ground beetles).

The mineral composition of chalk is dominated by calcite, which can be of both biogenic and autogenous origin; organic remains usually make up a significant part of the rock (up to 75%). In the main mass, they are represented by skeletal shells of planktonic algae-coccolithophores, as well as foraminifers (sometimes up to 40%). The size of skeletal remains is 5-10 microns. A variable, but sometimes significant value (10-90%) is powdered calcite with particles 0.5-2 microns in size, the content of larger particles in the form of microscopic calcite crystals is less significant. Occasionally in the Cretaceous there are shells of mollusks, skeletons of bryozoans, inocerams, remains of crinoids, sea urchins and lilies, flint sponges, and corals. In small quantities, usually up to 5, less often up to 10-12%, there are pelitomorphic non-carbonate impurities, mainly of terrigenous, less often of autogenous origin: quartz, feldspars, clay minerals (glauconite, kaolinite, hydromicas, montmorillonite), opal, chalcedony, pyrite and etc. Rarely and only in places there are concretions of flint, pyrite and phosphorite.

In the chalk strata, the development of large sustained cracks is observed - reservoir and vertical, filled with chalk flour. At the surface outcrops, the network of cracks is strongly concentrated. When chalk samples are impregnated with oil, hidden vein structures appear in them in the form of intertwining tiny cracks, as well as traces of numerous passages of worms - worms. In all Cretaceous deposits in different areas (horizons), chalk differs both in chemical composition and in physical and mechanical properties.
Density 2690-2720 kg/m3; porosity 44-50%; natural humidity 19-33%. When moistened, the strength of chalk begins to decrease already at a moisture content of 1-2%, and at a moisture content of 20-30%, the compressive strength increases by 2-3 times, while plastic properties appear. Natural chalk practically does not have frost resistance; after several cycles of freezing and thawing, it breaks up into separate pieces 1-3 mm in size.

According to physical properties and structural features, three types of chalk are distinguished: white writing; marl, characterized by greater density and less whiteness, due to the presence of clay substances; chalk-like limestone is a transitional difference from chalk to limestone.
Finding

Chalk is a semi-hardened silt of warm seas, deposited at a depth of 30 to 500 m. It is widely distributed in nature and is characteristic of deposits of the upper Cretaceous system and the Lower Paleogene, which is associated with the lush development of coccolithophores. Accumulations of white writing chalk are a specific feature of the Late Cretaceous and are found in almost all stages of the Upper Cretaceous, from the Cenomanian to the Massrathian inclusive. Chalk-like limestones are common in Tertiary deposits; in the Paleozoic, Cretaceous accumulations are not preserved, being transformed into various limestones.

The most significant band of chalk deposits is common in Europe, from the Emba River in Western Kazakhstan to Great Britain. Their thickness reaches several hundred meters (in the Kharkov region - 600 m). A powerful chalk belt extends across the entire European continent, including the north of France, the southern part of England, Poland, passes through Ukraine, Russia and moves to Asia - Syria and the Libyan desert. Chalk reserves are unevenly distributed over the territories: about 48-50% of high-quality chalk reserves with a high content of calcium and magnesium carbonate and a minimum content of harmful impurities are concentrated in Russia; about 32-33% in Ukraine and a little over 12% in Belarus. There are small deposits in Kazakhstan, Lithuania and Georgia. The total balance reserves of chalk in Russia are estimated at 3,300 million tons with unlimited probable reserves.

The reserves of the largest Sebryakovskoye (Volgograd region, Russia) chalk deposit for cement production are 890 million tons. Practically unlimited forecast chalk resources are concentrated in the Belgorod region (Russia), where 29 chalk deposits with total reserves of 1000 million tons have been explored, the largest of which are Lebedinskoye, Stoilenskoye and Logovskoye. At the same time, the Lebedinskoye and Stoilenskoye deposits account for 75% of the explored reserves of chalk in the Belgorod region. These two deposits are exploited for the extraction of iron ores, where chalk is the overburden. The chalk deposits of the Voronezh region belong to the Turoncognacian age. Chalk has a high content (up to 98.5%) and a low content of non-carbonate impurities (less than 2%), is enriched with amphora silica, chalk lies in close proximity to the surface and is covered with chalk eluvium or Quaternary deposits. A characteristic feature of the chalk deposit of the Voronezh region is its water saturation (moisture content reaches 32%, which causes serious difficulties in its extraction and processing).
Practical value

In industry, chalk is used for the production of lime, cement, soda, glass, school crayons. Used as a filler for rubber, plastics, paper, paints and varnishes. In agriculture, it is used for liming soils and feeding animals, in perfumery - for the preparation of toothpastes and powders. In the paper industry, it was used as a filler and bleach along with kaolin. Chalk is a necessary component of coated paper used in printing for printing high-quality illustrated publications. Ground chalk is widely used as a cheap material for priming, whitewashing, painting the walls of houses, and for protecting tree trunks from sunburn. The use of chalk as a filler and pigment in the production of paper and cardboard can be successful provided that the requirements for this type of raw material in terms of its optical properties and particle size distribution are met. The quality of chalk is mainly determined by its chemical composition and for many industries is regulated by state and industry standards; GOST 17498-72 "Chalk. Types of brand, basic technical requirements"; GOST 12085-73 "Natural chalk enriched (used in the rubber, cable, paint and varnish and polymer industry)"; GOST 8253-79 "Chemical precipitated chalk"; OCT 21-37-78 "Chalk and limestone for mineral nutrition of farm animals and poultry", etc.

The suitability of chalk for the production of lime and cement is determined by semi-factory tests. As of January 1, 1985, 219 chalk deposits with 1,680 million tons of chalk reserves, explored by industrial categories, were recorded in the USSR. In addition, 31 chalk deposits with reserves of 3,534 million tons were included in the balance of reserves of cement raw materials. Chalk reserves account for 12% of all reserves of carbonate cement raw materials. The reserves of the largest Sebryakovskoye (Volgograd region of the RSFSR) chalk deposit for cement production are 890 million tons. Deposits with chalk reserves of 20 million tons or more are considered large. Large reserves of chalk have France, Great Britain, East Germany, Denmark. In 1984, 75 deposits were developed in the CCCP (all open-pit) and 12.4 million tons were mined; in addition, 39.2 million tons were produced at 17 deposits of cement raw materials.

Zhigulevsky plant of building materials (Kuibyshev region of the RSFSR) artificially receives chemically precipitated chalk from limestone in the amount of 16.5 thousand tons per year. In the US, there are chalk deposits only in the central and southern states, but the chalk is of poor quality, so the US imports high grade chalk from France, Great Britain and Denmark.