Chalk deposit. Experimental determination of the physicochemical properties of chalk

White lump chalk, familiar to everyone since childhood, was presented to us by the ancient seas of the Cretaceous period. Its composition depends on the depth of reservoir formation - shallow or deep water. Despite the complete decrease in strength with high moisture, they are classified as hard semi-rocky rocks.

Its use is so wide that it is difficult to name an industry where it is not used as a raw material or auxiliary material.

What does it consist of

The composition of chalk includes shells of mollusks, silt, silicates, various admixtures that affect color and quality. Intact ancient fossils are sometimes found.

From the standpoint of chemistry, chalk consists of two parts:

1. The carbonate base includes about 99% calcium carbonates and 1-2% magnesium carbonate, which are soluble in acetic and hydrochloric acids.
2. Non-carbonate admixtures - metal oxides, clay, quartz sand and others, insoluble in acids.

How is it mined

Mining in progress open way in careers. The deposits differ in the thickness of the layers and in the content of calcium carbonate (calcium carbonate) CaCO3 and various impurities. It is the percentage that determines economic feasibility deep enrichment and its further application. If there are many impurities (sometimes more than 10%), chalk is used in agriculture to neutralize soil acidity or to produce lime. Although, for deposits Western countries, where the content of CaCO3 is 50-70%, is the norm.

The rock lies close enough to the surface, the thickness of the layers in different deposits ranges from 16 to 90 m, but the physical, mechanical and chemical properties of chalk at different horizons of the same deposit can differ significantly.

Simplified, the production process is as follows: from the quarry, the rock is delivered to the plant for drying in special installations at temperatures up to 400 ° C, crushers and mills are used to grind the pieces. The ground chalk passes through a fine grinder and a separator. The result is separated chalk.

Requirements are put forward for the product both in terms of the purity of the carbonate content in the composition and the fineness of grinding. Only modern equipment plants for the production of chalk products can provide the required quality.

Chalk properties

Physical

When moistened, chalk loses its compressive strength: at a moisture content of more than 30%, it acquires plastic properties. For this reason, the packaging should be marked: "Afraid of dampness."

Solubility - the property of a substance to dissolve in a liquid without forming a suspension, like sugar or salt. Chalk does not dissolve in water, but forms a suspension and subsequently precipitates.

The density of ground chalk is 2.6 g/cm3, bulk density is 950-1200 kg/m3.

Chalk is not at all frost-resistant, the process of freezing and thawing in a state saturated with water is not applicable to it.

Chemical

If an excess of oxygen is present, the CaCO3 carbonate reacts to form Ca(HCO3) bicarbonate, which gives hardness to the water.

When CaCO3 is calcined in the temperature range from 900 to 1200°C, it decomposes into carbon dioxide and air lime CaO - this is how chalk differs from lime. Quicklime is a product obtained by firing chalk, shell rock or limestone.

A question from the school curriculum: how to distinguish chalk from slaked lime, if both substances are already in the form of suspensions for coloring? We recall: chalk reacts with vinegar, releasing carbon dioxide - in which container the characteristic reaction will go, it will be there.

Where is chalk used

The use of chalk in any area of ​​industry is due to its categories, which depends on the percentage of carbonates.

• 1 - pure chalk (MMO, MKB-1, MM-1, MMS-1, MMS2, MMSP, MMSG-2);
• 2 - slightly clayey (MK-2, MM-2),
• 3 - strongly clayey (MK-Z, MM-Z),
• 4 - marl-like (MMIP-1, MMIP-2, MMZHP, MMPC).

According to the standards, brand lettering and application by industry are as follows:

• MK - lumpy,
• MM - ground,
• IN - for calcareous soils,
• ZHP - for feeding farm animals and watering,
• PC - production of animal feed,
• C - separated,
• SG - separated hydrophobized,
• Oh - enriched.

By this marking on the packaging or in the catalog, you can determine the purpose and quality of the material.

How serious the requirements are for individual brands, as for raw materials, can be seen from the following GOST notes:

• for use in the paint and varnish and polymer industry, indicators of the reflection coefficient are additionally set;
• for use in the cable industry, the proportion of free alkali is limited.

Where is it used in construction

Building chalk is sold both in pure form and in dry mixtures. Lumpy grades MK-1, MK-2, MK-3 are intended for construction.

• The cheapest "staining" water-based paint is whitewash chalk, the color of which was added with blue linen. With the advent of PVA glue, they began to add it to fix chalk in the paint layer - this is how the prototype of water-based paint appeared.
• Adhesive putty for walls was prepared immediately before application, one of its compositions: drying oil, adhesive solution, chalk.
• Viennese white, which is based on chalk, is the most famous glue paint.
• The addition of drying oil to the chalk made it possible to create the famous putty on the glass of wooden windows.
• Finely dispersed chalk is used as a filler in plastics and paints to save the main raw materials and ensure such qualities as strength, fire resistance, color, wear resistance and others.

Is chalk harmful? Perhaps this is one of the most environmentally friendly and harmless building materials.

Chalk- it is a soft mountain porous sedimentary rock white color, is a type of limestone and is composed of the mineral calcium (calcite), which is also called calcium carbonate or CaCO3. It is formed at sea depths with the accumulation of small plates of calcite. The chalk contains a large number of magnesium carbonate and metal oxides.

Chalk has a very greater weather resistance than clay, with which it is commonly associated, thus forming high, steep cliffs where the chalk ridges meet the sea. Chalk mounds tend to form where chalk streaks reach the surface at an angle, thus forming a cliff. Since chalk is porous, it can contain a large amount of ground water, providing natural reservoirs that release water slowly due to dry seasons.

1. Clusters
2. Education
3. Compound
4. used

Chalk accumulations

The Cretaceous group of the European stratigraphic division originated during the Cretaceous period. It forms the famous White Cliffs of Dover in Kent (England), as well as the white slopes on the other side of the Strait of Dover. In Champagne (France), chalk caves are used to store wine. Some of the highest chalk cliffs in the world occur in Mons Klint (Denmark).

Chalk formation

Ninety million years ago Northern Europe silt accumulated in the lower part of the great sea. Protozoa, such as foraminifera, lived on marine debris that fell down from the upper layers of the ocean. Their particles were made from calcite extracted from sea water.

Chalk composition

Chalk consists mainly of calcium carbonate (over 98%) with small amounts of silt and clay.

Chalk used

It is used in the production of quicklime and slaked lime, as a whitewash for buildings and tree trunks. In southeast England, Danehole is a prime example of ancient chalk quarries. In such places, flint was mined, which was then used in the manufacture of stone tools.

They write with chalk on school boards, mostly rough. Although natural chalk is traditionally used, modern blackboard chalks are usually made from the mineral gypsum (calcium sulfate), often supplied in compressed powder sticks about 10 cm long.

Sidewalk chalk is similar to school chalk, although it is larger and more colorful. It is used to paint on sidewalks, streets and roads. This is done mainly by both children and adult artists.

In agriculture, chalk is used to increase the pH in soils with high acidity. The most common forms are CaCO3 (calcium carbonate) and calcium oxide.

In tennis, chalk used to be used to mark the playing field. This has the advantage that if the ball hits the line, a cloud of chalk or pigment dust can be seen. Chalk has now been replaced by titanium dioxide.

In gymnastics, climbing, weightlifting and tug of war, chalk - now commonly magnesium - is applied to the hands to remove sweat and reduce slip.

Tailor's chalk is tough and is used to make temporary markings on fabrics. Nowadays, it is usually made from talc (magnesium silicate).

Toothpaste also usually contains a small amount of chalk to serve as a mild abrasive.

Chalk is used for very fine polishing of metals.

Chalk is a source of quicklime by thermal decomposition or slaked lime by quenching with water.

Who among us does not know chalk? Whose pockets and fingers were not soiled by a piece of light stone the color of snow in childhood? Who does not know happiness artistic creativity"Cretaceous" period? Who, as a teenager, did not investigate the properties of chalk in "bubble" experiments, did not examine a chalk smear under a microscope?

mineral chalk- a witness to eras that have passed tens of millions of years ago. Awareness of this fact changes the perception of familiar material. Having a biological origin, the chalk stone learned its properties from organisms that lived in ancient times.

Origin of chalk

The Cretaceous period is a period of time covering about 80 million years during the reign of dinosaurs. Warm and shallow (30-500 meters deep) seas of that time gave shelter to myriads of the smallest mollusks that built their skeletons and shells from calcium extracted from the water.

The remains of these creatures, accumulated in bottom sediments in multi-meter layers, turned into the well-known chalk. In percentage terms, the mineral chalk is divided into the following parts:

• fragments of skeletons - about 10%. We are talking not only about the simplest creatures, but also about multicellular animals endowed with the ability to extract and concentrate calcium salts in tissues.

• shells of microscopic mollusks foraminifera - about 10%. However, not all rhizopods (the Russian name for animals) had a calcareous shell. Some built their protective layer from a chitin-like substance. In many ways, therefore, in the Cretaceous deposits of calcium carbonate itself, no more than 98% (and no less than 91%) are found.

• fragments of calcareous growths of algae - up to 40%. Coccolithophores - the plant plankton of the oceans - feel great in our time. Up to 98% microscopic living suspension in upper layers seas accounted for and accounts for this type of algae. Therefore, the calcareous mineral, in fact, is a product for the most part of plant rather than animal origin. The origin of chalk is the merit of plants!

• finely dispersed crystalline calcite - up to 50%. We are talking about "fragments of debris", and so miniature in size that it is not possible to determine their biological affiliation.

• insoluble minerals (mainly silicates) - up to 3%. This is mainly geological debris (sand and fragments of various rocks) brought into the Cretaceous deposits by winds and currents. Although, in addition, biogenic calcium formations are enriched with phosphorus and silicon compounds during metabolic processes during the life of the animal.

Shells of more or less large mollusks, skeletons of coelenterates, concretions of alien minerals are relatively rare in the Cretaceous strata. Only a few photographs of chalk show the observer arrays dotted with cavities of bulk shells.

Chalk composition

It is assumed that chemical formula chalk corresponds to the formula calcium carbonate CaCO3. However, the real composition of chalk differs from the composition of the calcium salt of carbonic acid.

Actually, calcium oxide in the mineral is about half: the concentration of CaO ranges from 47% to 55%. There is also a lot of carbon dioxide in the chalk, which is in bound state. CO2 - up to 43%!

Magnesium oxide MgO can reach up to 2% of the total mass of chalk. Inclusions of quartz SiO2 are usually not too significant, but in general are mandatory, and can reach a concentration of 6%. The density of chalk with a high silicon content is greater than normal.

Somewhat less in the composition of chalk aluminum oxide Al2O3 - no more than 4%. A variety of iron oxides rarely exceed the half-percent concentration threshold, but it is they that color the chalk red quite often.

Chalk application

Like an independent construction material chalk is used only as a raw material for the production of chalk paints. Out of mass use half a century ago, the whitewashing of rooms with a colloidal solution of pure or colored chalk is almost never done today.

As a masonry stone, chalk is untenable - although the premises dug into the chalk massifs remain habitable for centuries. The low hardness of the chalk makes it possible to gradually excavate the stone without large-scale destruction of the massif.

In the construction industry, the use of chalk is growing and expanding. Production of cement and glass without chalk is almost impossible! Chalk is required by paper-making enterprises, light industry, and organic chemistry. Paints and rubber, hygiene products and soil fertilizers, animal feed and perfume compositions are produced using chalk.

Can you eat chalk?

It is known that with a lack of calcium in the body, a craving for eating chalk can develop. The experience of generations that grew up in conditions of organic calcium deficiency says: chalk is edible! However, doctors, answering the question whether it is possible to eat chalk, are not so unambiguous.

The properties of chalk change dramatically under the influence of gastric juice. Chalk, which has passed through the crucible of oxidative processes, loses its original neutrality and becomes a chemically active reagent. In effect, it is similar to slaked lime. The mucous membrane of the digestive tract suffers from contact with oxidized chalk.

In addition, the concentration of calcium in the chalk is excessively high. Eating chalk can provoke liming of blood vessels. It is much safer for calcium deficiency to pay attention to medical preparations this metal. A tablet of calcium gluconate affects the body much more positively than a piece of eaten chalk.

Stationery, construction and even fodder agricultural chalk are not suitable for human consumption! A person does not have the opportunity to safely (and even more so for his own benefit) process and assimilate this mineral!

Cretaceous deposits of Eurasia stretched in a wide strip from the Kazakh river Emba to the western tip of Britain. The deposits reach the greatest thickness south of Kharkov: here there are real chalk mountains with a massif thickness of up to 600 m. The ongoing development of the white mineral promises scientists many new discoveries.

Chalk- this is not only a familiar subject from school times, but also a witness to eras that have passed millions of years ago.

Most of the composition of the chalk is formed by calcium deposits of the shells of prehistoric microorganisms and protozoa. Cretaceous deposits, including processed ones, are used today in various fields - from the production of paints and food additives to cosmetics.

How did chalk come about?

Chalk is an natural material and is mined as a mineral. Basically, it is calcium deposits formed from the remains of ancient terrestrial organisms.

In the production of chalk and chalk-containing products, already processed chalk is used.

Natural chalk deposits often contain various undesirable impurities - stones, sand and various mineral particles. Therefore, the chalk mined in the deposits is broken and mixed with water in such a way as to obtain a suspension.

At the same time, heavy impurities sink to the bottom, and light calcium particles are sent to a special tank, where, after adding a special adhesive, they are dried, turning into chalk, which can be painted on.

Raw chalk from chalk quarries used for construction purposes to obtain lime.

We bring to your attention another article about the origin, its composition and medicinal properties.

What is chalk and what does it consist of?

Chalk contains:

• calcium oxides - from 47 to 55%;
• carbon dioxide - up to 43%;
• silicon dioxide - no more than 6%;
• aluminum oxide - up to 4%;
• magnesium oxide - no more than 2% of the total mass of chalk;
• chalk may also contain iron, however, its concentration usually does not exceed 0.5%.

Chalk accumulations

The accumulation of Cretaceous deposits began in the so-called Cretaceous period, covering a period of 80 million years. About 20% of the Earth's sedimentary rocks include chalk.

Chalk deposits:

• To the largest chalk deposits include the White Cliffs of Dover, the chalk caves in the French city of Champagne and the chalk cliffs of Mons Klint in Denmark.
• On Russian territory Cretaceous mountain deposits up to 600 meters thick are located south of Kharkov.
• The largest deposits of the Voronezh region- Kopanischenskoe, Rossoshskoe and Buturlinskoe. The city of Belgorod, presumably, got its name from the local chalk deposits.

Chalk formation

The formation and accumulation of limestone deposits took place over eighty million years.

foraminifera- single-celled organisms, the shells of which served as the basis for the formation of today's Cretaceous deposits. After the death of these protozoa, their shells sank to the bottom of the ocean, creating foraminiferal limestones.

These formations, along with the remains of unicellular coccolithophorid plants, are an integral part of today's Cretaceous accumulations. Compressed under water pressure, the remains of coccolithophores and shells of ancient mollusks have been supplemented by the skeletal remains of fish and animals for millions of years.

Despite the fact that back in 1953 scientists announced the predominant role of plants in the formation of limestone rocks, among the inhabitants there is still an opinion about the primacy of foraminifers.

Compound

Cretaceous deposits include:

• Skeleton fragments– approximately 10%. These are the remains of not only protozoa, but also large multicellular animals.
• Shells of ancient molluscs- ten %. Among them were animals with limestone shells - foraminifera.
• Particles of calcareous growth of algae- no more than 40%. Most of the limestone deposits, contrary to popular belief, were formed from the remains of the simplest plants - coccolithophorids, and not from the shells of foraminifers. Coccolithophores have not died out, they feel great in the vastness of the world's oceans today, taking part in the exchange of carbon between the ocean and the atmosphere.
• Crushed crystalline calcite- no more than 50%. These are natural mineral formations of complex origin.
• Insoluble silicates- until 3%. These are minerals of geological origin - sand, fragments of rocks brought into the chalk deposits by wind and water. Properties of chalk

Humidity, which affects its strength and plasticity, has a great influence on the properties of chalk. An increase in humidity leads to deformation, while in a dry environment, chalk can crumble even from slight pressure.

Moisture-saturated rock sticks to construction tools. That's why construction works using calcium carbonate is carried out in countries with a hot and arid climate. An excellent example of an ancient limestone building is the Egyptian pyramid of Cheops (Khufu).

At sub-zero temperature the rock is prone to disintegration into fragments of a few millimeters.

Chalk cost

The price of chalk will depend primarily on its type (processing) and purpose:

• for drawing on asphalt will cost no more 200-400 rubles for packing.
• white crayons without dyes will cost about 100 rubles .
• farm chalk I buy in large quantities, shipping it in several tons. The cost of each ton of ground chalk is 3000-5000 rubles.
• Price for food chalk used in medicine and food supplements (E-170) - from 40 to 300 rubles for 100 grams. The stone was also used in medicine).

Chalk application

Today, chalk is a fairly widespread material for various industries.

So, chalk is used in the following areas:

1. Chalk paints applied to interior decoration during construction and renovation works.
2. Chalk is included cement mixtures providing them with softness and elasticity.
3. Ground natural chalk actively used for glass production.
4. Chalk is part of the farm feed and is used to fertilize the soil.
5. Chalk is the basis for cosmetics- lipstick, foundation, powder, etc. It is the chalk in the composition of the foundation that absorbs excess fat and protects the skin from shine.
6. Chalk is also used for domestic purposes as an absorbent and whitening agent.
7. Production of tooth powders and pastes also not without the use of chalk.
8. In the production of paper and cardboard products finely dispersed (crushed) chalk is used as a filler and bleach for paper. Chalk treated with stearic acid has hydrophobic properties. It is also used in paper industry. The content of chalk in paper improves print quality and reduces the likelihood of wear and tear of printing equipment.
9. Not so long ago, chalk was used to mark the playing field.. The suspension rising into the air after the ball hit the line was easy to see. Today titanium dioxide is used instead of chalk.
10. To remove sweat and reduce the risk of slipping, chalk is used in sports such as weightlifting, gymnastics and rock climbing today.

Can you eat chalk?

A lack of calcium and other beneficial trace elements can lead to a desire to eat chalk. During pregnancy, with anemia, some people have a strong craving for eating chalk, so the question of the safety of this mineral for the body arises for many.

Of course, one or two small pieces of pure chalk will not bring much harm to the body. However, it must be remembered that chalk without impurities is not available for free sale and it is practically impossible to get it, except perhaps in the pharmacy in the form of calcium gluconate. In the most common product - "school chalk", during the production they add glue and various dyes that are toxic to the body.

The use of chalk in large quantities can cause liming of blood vessels, the formation of kidney stones and provoke problems with the digestive tract.

In addition to the detrimental effect of impurities that make up construction and chancellor chalk, it is characterized by oxidation when interacting with gastric juice, which turns it into a harmful chemical reagent.

What to do if you want to eat chalk?

The desire to eat chalk is often a signal of a lack of calcium in the body. The reasons for its deficiency can be a monotonous diet, long-term stressful conditions, weakening of the body after serious illnesses and pregnancy.

Given that during pregnancy it is calcium that is the basis for the formation of the nervous and skeletal system of the child, the lack of this mineral must be filled. In this case, a variety of diet is not able to completely solve the problem, so doctors strongly recommend taking special vitamin complexes during pregnancy.

Due to the fact that the neural tube of the fetus is formed on early dates, in order to minimize the risks of improper development, it is necessary to start taking vitamins even during pregnancy planning. Anemia and calcium deficiency in the body often appear with heavy and long periods.

With symptoms of severe calcium deficiency (convulsions, marked deterioration and blanching of skin and hair) you can take calcium gluconate tablets. Unlike stationery and other types of industrial chalk, they are safe, however, with prolonged use they can lead to constipation.

As a rule, the craving for eating chalk ends after the diet is expanded to include dairy products, chicken eggs and fresh greens.

In some cases, the desire to eat inedible and inedible substances can be a sign of a mental disorder. Consequence of the use of inedible objects are intestinal obstruction and nutritional deficiencies.

Chalk is a white sedimentary rock. It is insoluble in water and is of organic origin. From the article we learn where chalk is used, the physical and chemical properties of this rock.

Education

90 million years ago in Northern Europe, in the lower region of the great sea, silt accumulated. Protozoa (foraminifera) lived on marine debris. Their particles included calcite extracted from water. The Cretaceous group of the stratigraphic European division appeared during the period of the same name. From it formed in Kent and slopes in another part of the Strait of Dover. It was these remains that became the basis of the chalk. However, the rock mainly consists of formations of algae and finely dispersed compounds. Thus, the researchers conclude that the appearance of chalk is the merit of plants.

Rock structure

The remains of mollusks that accumulated in bottom sediments turned into chalk. The breed contains:

1. About 10% of skeletal debris. Among them are not only parts of protozoa, but also multicellular animals.
2. About 10% of foraminifera shells.
3. Up to 40% fragments of calcareous algae formations
4. Up to 50% crystalline fine calcite. Its size is so small that it is practically impossible to establish the biological identity of the elements that make it up.
5. Up to 3% insoluble minerals. They are mainly represented by silicates. Insoluble minerals are a kind of geological debris (fragments of various rocks and sand), which is brought into the chalk deposits by currents and winds.

Mollusk shells, concretions of other minerals, and skeletons of coelenterates are found quite rarely in the rock.

Description of the physical property of chalk - strength

Studies of the substance were carried out by many scientists. In the course of engineering and geological measures, it was revealed that it is a rigid semi-rocky rock. Its strength is largely determined by moisture. In the air-dry state, the compressive strength varies from 1000 to 45,000 kN/m 2 . dry rock - from 3 thousand MPa (for a loose state) to 10 thousand MPa (for a dense one). The value of the angle of internal friction is 24-30 degrees, with all-round compression, the adhesion reaches 700-800 kN/m 2 .

Humidity

When exposed to water physical properties the chalk begins to change. In particular, its strength is reduced. Changes occur already at 1-2% humidity. At 25-35%, the compressive strength increases by 2-3 times. Along with this, other physical properties of chalk appear. The rock becomes plastic. This manifestation significantly complicates the process of processing the substance. During this, the chalk begins to stick to the elements of the machines (on the excavator bucket, feeder, body vehicle). Often, the physical properties of chalk (viscosity and plasticity) do not allow mining from lower horizons, although here it is considered to be of high quality.

Frost resistance

After freezing-thawing, the chalk breaks up into particles 1-2 mm in size. In some cases, this is a useful property of the breed. For example, when it is used as an ameliorant during soil deoxidation, it is not necessary to grind the substance to 0.25 mm. Crushed rock up to 10 mm can be introduced into the soil. When freezing-thawing with plowing the soil, the pieces are destroyed by themselves. Thus, the neutralizing effect is maintained for a long time.

Chalk Properties: Chemistry

The rock mainly includes carbonate and non-carbonate parts. The first is soluble in acetic and hydrochloric acids. The non-carbonate part contains metal oxides, quartz sand, marls, clays, etc. Some of them are insoluble in these acids. The carbonate part contains 98-99% calcium carbonate. Crystalline particles of magnesian calcite, siderite and dolomite are formed by magnesium carbonates, which are included in chalk in small amounts. The composition and properties of the rock act as classification criteria.

Identification of quality deposits

Initially, it was believed that the mechanical and chemical properties of chalk are the same throughout the deposit. However, in practice, during the long-term operation of the region, especially after the transition of the mining and processing enterprise to the production of higher quality products, differences in these characteristics are revealed. Therefore, geological and technological mapping is carried out at some fields. Researchers, studying the chemical properties of chalk and its mechanical characteristics in different parts of the deposit, designate areas of accumulation of high-quality rock.

Industrial development

Large deposits of chalk are present in the Belgorod and Voronezh regions. Less quality substance present in Znamenskaya, Zaslonovskaya, Valuyskaya and other deposits. Relatively low rates of CaCO 3 (no more than 87%) are revealed at these deposits. In addition, various impurities are present in the rock. Therefore, high-quality products cannot be obtained at these deposits without deep enrichment. The physical properties of chalk on such deposits make it possible to use it in the manufacture of lime, as well as in land reclamation measures to deoxidize soils. The Voronezh deposits are attributed to the Turonian-Coniacian age. Higher quality chalk is mined here. The properties and application of the rock obtained from these deposits have been studied for a long time. The product mined in the Voronezh region has a high CaCO 3 content (up to 98.5%). The proportion of non-carbonate impurities is less than 2%. Mining at the deposits, however, is hampered by the physical properties of the chalk. In particular, its high water saturation. The proportion of moisture in the rock is about 32%.

Promising deposits

Among the large deposits, it is worth noting Rossoshanskoye, Krupnennikovskoye, Buturlinskoye and Kopanishchenskoye. The chalk thickness of the latter is 16.5-85 m. The overburden is the soil-vegetative layer. Its thickness is about 1.8-2 m. The chalk layer is divided into two units along the vertical line. At the bottom there is up to 98% calcium carbonate, at the top it is slightly less - up to 96-97.5%.

An extremely homogeneous mineral was found in the Buturlinskoye field. white chalk Turunian stage. The thickness of the layer is 19.5-41 m. The overburden thickness reaches 9.5 m. It is represented by margels, vegetation layer, sandy-clayey formations and sandstones. The share of magnesium and calcium carbonates reaches 99.3%. At the same time, non-carbonate components are present in a relatively small amount.

Of great interest to industry are the Stoilenskoye and Lebedinskoye deposits. In these areas, chalk is mined as overburden and taken to dumps. The associated annual production is more than 15 million tons. About five of them are used in the national economic sectors. In particular, chalk is supplied to the Starooskol cement plant and some other small enterprises. Most of the mined rock is lost in the dumps.

Chalk, which is located in areas of iron ore deposits, is classified as high-quality in terms of silica and carbonate content. It can be used for industrial purposes without deep enrichment. It must be said that in the process of designing mining and processing enterprises specializing in iron ores, it is necessary to provide for technological lines for the incidentally extracted chalk or a place for its separate storage.

Production and consumption

Beneficial features chalk has been known for a long time. Initially, the breed was used in construction. Lime was made from it. Chalk powder acted as the basis for putty, fillers, paints and so on. At the end of the 19th century, private factories began to be organized at the White Mountain deposit. Lime and powder were produced from lumpy rock. In 1935, the Shebekinsky plant appeared, which was engaged in the production of products for industrial needs. Useful properties of chalk were in demand in the electrical, paint, polymer, rubber and other industries.

Along with the increase in the demand for products, the requirements for its quality increased. The enterprises that existed by 1990 could not provide the industry with the necessary raw materials. Private enterprises began to appear in the Belgorod region. Their large number was due to the huge volumes of rock deposits and the apparent simplicity of processing technologies. However, the primitive methods of extraction and subsequent processing used by private enterprises could not provide required amount quality products. Accordingly, many such factories closed. At the same time, large enterprises have modernized and reconstructed their equipment. The release of quality products was provided in the 90s by the Belgorod, Petropavlovsk, Shebekinsky plants.

Production of quality brands

The key requirements for chalk products, in addition to the proportion of carbonates, include fineness - fineness of grinding. It is expressed as a residue on sieves of a certain size or as a percentage of particles of a given size (for example, 90% of particles with a size of 2 microns).

The emergence of new production lines for the manufacture of paint, rubber, polymer and other products for which chalk is used as a raw material provoked a sharp imbalance between its production and consumption. This was especially evident in the paper industry. Enterprises in this industry have special requirements for chalk powder, which has replaced kaolin in production.

The production of high-quality brands is concentrated at factories in the Belgorod region. In addition to the Shebekinsky enterprise, which produces separated chalk, new plants were created. So, in 1995, a processing plant appeared at Lebedinsky GOK - ZAO Ruslime. It was built according to the Spanish project of the company "Reverte" with an estimated capacity of 120 thousand tons / year. The plant produces up to 10 different grades of chalk. In terms of quality, they are in no way inferior to foreign counterparts and meet international standards. The company is equipped with the most modern technological equipment, line operations are mechanized and automated.

According to the project of the Mabetex company, a plant with a capacity of chalk products was built at Stoilensky GOK High Quality 300 thousand tons. At the same time, the plans of the enterprise provide for a subsequent increase in capacity.

Breed blooming

One of key criteria in the process of analyzing the physical properties of the rock at a new field or area involved in an existing production line processing, is the behavior of chalk when crushed. As mentioned above, in different reservoir layers, the substance has different mechanical characteristics. Visually identifying these differences is not possible in most cases. Determination of the behavior of chalk during its dry grinding in technological process is carried out by establishing an indicator of its blooming in a humid environment under mechanical action. For this, special equipment is used.

sodium bicarbonate

For its production are used different materials, including limestone or chalk. The beneficial properties for the body that sodium bicarbonate possesses are known to many. Often it is used for diseases of the gums and throat, heartburn, to thin sputum when coughing. In industry, the physical properties of soda and chalk are in great demand. Both of these substances are used in construction, decoration, materials, paints and other products. With regard to the production of calcium bicarbonate, the use of chalk alone is considered an uneconomical option. As mentioned above, this rock absorbs moisture very well, as a result of which its mechanical characteristics change. This, in turn, negatively affects the course of the technological process.

Is it possible to eat CaCO 3?

It is widely believed that doctors recommend using medical chalk. The properties of this substance are believed to help replenish calcium deficiency. First of all, it should be said that doctors are ambiguous about this. Often, patients who like to eat chalk (food) turn to specialists. Useful however, are rather doubtful. Cravings for eating it may occur due to a lack of calcium. However, you should be aware that the characteristics of the substance undergo significant changes when it enters the stomach. Passing through several oxidative processes, it loses its original neutrality and turns into a reagent. In its action, the substance is similar. As a result, oxidized chalk begins to influence the gastric mucosa. Medicinal properties none of them show up. Rather, on the contrary. It is worth remembering that the concentration of calcium in the substance is very high. As a result overuse chalk can provoke liming of vessels. In this regard, doctors recommend replacing it with calcium gluconate or similar drugs. As for getting rid of heartburn, according to many people who have tried to eliminate it with chalk, it does not help in this.

Industrial and domestic use

Mel acts as required component paper used in printing. The high dispersion of calcium carbonate in crushed form affects the optical and printing characteristics, porosity, and smoothness of products. Due to the presence of chalk, the abrasiveness of products decreases. The ground rock is widely used for whitewashing walls, borders, and protecting trees. Chalk is used in the purification of beet juice, which, in turn, is used in the match industry. For these purposes, as a rule, the so-called precipitated rock is suitable. Such chalk is obtained by chemical means from calcium-containing minerals. Along with other carbonate rocks, the substance is used in glass melting as one of the charge components. Due to the chalk, the thermal stability of the product, its mechanical strength and stability when exposed to weathering and reagents are increased. The breed is widely used in the manufacture of fertilizers. Also, chalk is added to feed for farm animals.

Rubber industry

Chalk is in first place among all the fillers used in the industry. This is primarily due to the fact that the use of this raw material is economically beneficial. Chalk has a relatively low cost. At the same time, its introduction into rubber products does not cause harm. The second reason for the popularity of raw materials in the industry is technological expediency. Chalk greatly simplifies the process of manufacturing rubber products. In particular, due to it, vulcanization is accelerated, the surface of the products becomes smooth. The breed is also widely used in the production of sponge and porous rubber, plastic products, leather substitutes, and so on.