Blog – Sand mining in Russia – where and how is sand mined?! Origin, types and extraction of clay How clay is mined in the summer.

Clay has been known to mankind since ancient times and is actively used in economic activity. In our article we want to talk about its types and how clay is extracted.

Origin of clay

Before starting the conversation, I would like to define the breed. What is clay? It is a sedimentary fine-grained rock that has a dust-like structure when dry and plastic when moistened.

It is formed as a result of the destruction of rocks, for example, during the process of weathering. The main source of clay layers is feldspars. It is when they are destroyed under the influence of atmospheric reagents that clay minerals are formed. Sometimes strata are formed through the process of accumulation. But more often this occurs as a result of sediment from water flows. Then accumulations of clay form on the bottom of seas and lakes.

Types of clay

Sedimentary clays are formed as a result of the transport of clay weathering products to a new place and settling there. Based on their origin, such rocks are divided into continental (formed on the mainland) and marine (formed on the seabed).

In turn, marine clays are divided into:

1. Coastal-marine. They form in coastal regions, river deltas and bays. They are characterized by unsorted material. Very often such rocks are interbedded with siltstones, sandstone, and coal seams.
2. Lagoon. Such clays are formed in sea lagoons (desalinated or with a high salt concentration). As a rule, the rocks contain iron sulfides and calcites. Among them there are fire-resistant types.
3. Offshore. Such clays are formed at a depth of no more than 200 meters. They are more homogeneous in composition.

But among the clays of continental origin there are:

1. Diluvial, which are characterized by a mixed composition and its sharp change.
2. Ozernye. Such rocks contain all clay minerals. It is believed that the best types of fire-resistant species belong to lake clays.
3. Proluvial. Such rocks are formed by temporary flows. They are characterized by poor sorting.
4. River species can be found on the terraces of reservoirs, especially in the floodplain. Such rocks are poorly sorted and quickly turn into pebbles and sands.

In addition, residual clays are released. They are formed as a result of weathering of all kinds of rocks on sea or land. Usually they are not very flexible. Continental residual rocks include kaolins and other eluvial clays.

In Russia, the extraction of clay (ancient residual rocks) is quite common in Eastern and Western Siberia and the Urals.

Is the earth rich in clay?

Clay is found in many regions of the globe. If there is not much black gold and diamonds on Earth, then there is certainly plenty of clay. This is quite natural, since the rock is sedimentary and, in fact, is stones worn out by time and external factors, crushed to a powder state. Clay is home to a variety of organisms that affect its color. Iron salts play an important role in the coloring of the mineral. In nature, there are pink, green, blue, yellow, red and other clays.

IN old times Clay mining was carried out along the banks of lakes and rivers. They also dug special pits for mining. Then it became easier to purchase the mineral from a potter than to mine it yourself. Of course, extracting red clay is not a difficult task. But, for example, noble white previously could only be purchased in special stores for artists. Currently, you can purchase the mineral in the form of a cosmetic product in any store. Of course, such clay is not sold in its pure form, but with all sorts of additives.

We encounter clay in everyday life almost every day. Field paths and paths are covered with a layer of dust in the heat; in the rain they turn limp, like slurry, because there are minerals here too.

Properties of clay

The widespread extraction of clay (photos are given in the article) is directly related to its properties, since it has long been used by people for a variety of purposes. When dry, it absorbs water perfectly, and when wet, it does not allow moisture to pass through at all. As a result of mixing and kneading, clay can take on a variety of shapes, retaining them even after drying. This property is called plasticity.

In addition, clay has good binding ability with solid and powdery bodies. As a result of mixing with sand, a plastic mass is obtained. However, its plasticity decreases with increasing sand and water content in the mixture.

"Skinny" and "fat" varieties

Clays are divided into “lean” and “fat”. The latter have a high degree of plasticity. And they got the name “fat” because when soaked they feel greasy to the touch. This clay is slippery and shiny, it contains few impurities.

The extraction of sand and clay is always inextricably linked, since, as a rule, a mixture of them is used. For example, when producing bricks from fatty clay, many cracks form during firing. To avoid such unpleasant moments, sand (sometimes sawdust, brick fragments) is added to the clay.

Minerals that are not plastic or have low plasticity are called “lean.” They are rough to the touch and have a matte surface. When rubbed, such clay easily crumbles, since it contains a lot of impurities. A brick made from such a mineral is not durable.

A very important property of clay is its relationship to firing. As you know, when soaked, it hardens in the sun. However, it can be easily crushed into dust. But after firing, the clay changes its internal structure. At very high temperatures, clay can even melt. It is the melting point that characterizes the refractory properties of a substance. Different varieties Clays have completely different refractory properties. There are types of minerals that require enormous heat for firing (about 2000 degrees). Such temperatures are difficult to achieve even in factory conditions, so there is a need to reduce fire resistance. This can be achieved by introducing additives (lime, iron oxide, magnesia). They are called fluxes.

Clay has different colors (white, yellow, bluish, brown, red, etc.). The quality of the brick in no way depends on the shade of the mineral.

Use of clay for medicinal purposes

Some types of clay are used in medicinal purposes. White is used to treat obesity, intestinal diseases, hair loss, and strengthen nails. Red is used for cardiovascular diseases, varicose veins, hypotension, endocrine and nervous diseases. Yellow clay helps with osteochondrosis, headaches, problems with the intestines and stomach.

Black is used to lower fever, for treatment inflammatory diseases skin, to rejuvenate the body. But blue clay is used to treat obesity, hypothyroidism, relieve muscle weakness and improve joint mobility. In cosmetology, this type of clay is used for oily skin.

Industrial Applications

Clay is actively used in industry: in the production of ceramic dishes, tiles, earthenware and porcelain sanitary ware. The mineral is no less in demand in construction. Clay is used in the production of bricks, building materials and expanded clay. It is also the basis for all brick and pottery production. When mixed with water, clay forms a plastic dough-like mass that can be processed. The initial properties of raw materials can vary significantly depending on the place of origin.

Natural red clay owes its color to the presence of iron oxide in its composition. When fired, depending on the type of kiln, it may acquire a whitish or red tint. It is actively used for making small sculptures.

White clay is quite common in the world. When wet, it has a light gray color. But after firing it acquires a noble shade of ivory. This type is incredibly plastic due to the absence of iron oxide in the composition. White clay is used to make tiles, dishes, plumbing fixtures, and crafts.

To produce porcelain objects, a special type of clay is used, which contains quartz, kaolin and feldspar, but iron oxide, on the contrary, is absent. When wet, the mineral has a light gray tint, but after firing it becomes white.

Clay: extraction method

There are a variety of ways to extract the mineral. It all depends on the volume of inventory and location. As you know, there are quarries for clay extraction, in which the extraction of minerals from the massif is carried out by gear hobbing machines or excavators.

For large volumes of rocks, especially if work is carried out in winter time, use the explosive method. The extraction of clay and kaolin (blue, white clay) in conditions of high quarry humidity or at kaolin factories is carried out using hydraulic monitors.

For ceramic enterprises, the rock is mined in specially designed quarries, after which it is transported by rail and road to its destination. As a rule, several types of clays occur in a rock layer. Each variety is removed separately.

Place of Birth

Natural accumulations of rocks are called deposits. The territory of Russia is rich in reserves of various types of clays. For the ceramic industry, deposits of pure rocks that contain few impurities are of great interest. They belong to kaolin and refractory clays. Mining of ordinary (light-melting) varieties in Russia is carried out almost everywhere. But deposits of refractory and blue clay are much less common.

Clay mining in Russia is carried out in such deposits as Kashtymskoye, Nevyanskoye, Astafievskoye, Palevskoye. Each of them has its own characteristics depending on the conditions of formation, chemical and mineral composition.

Deposits of fire-resistant species are much more common than kaolin deposits. But at the same time, the most numerous are the places where refractory varieties are adjacent to fire-resistant ones. In Russia, the most famous among them are the Troshkovskoye, Latnenskoye and Gzhelskoye deposits.

But the main places for bentonite production are the Gumbrian, Aksan and Oglalinskoye deposits.

The location for clay extraction is always chosen depending on quality indicators raw materials, volumes of reserves and economic benefits of their development.

Instead of an afterword

Since ancient times, people have used the properties of clay for their own purposes. Its extensive reserves make it possible to use it without hesitation in various industries and in everyday life.

Sand is an important construction material used in a variety of processes during construction. The volume of its consumption on an industrial scale is several times higher than the use of crushed stone and other non-metallic building materials. That is why sand extraction and the constant development of existing deposits are important.

For work performed by residents in everyday life, sand is easy to find, as it is found on roads, agricultural lands and other in public places. But in order to use the material in industrial quantities, you need to know how the process is carried out correctly and be guided by strict rules on extraction technology and further transportation.

Registration of business law

Sand is of natural origin and is mined in special quarries. As a rule, mining sites are sandy or with an admixture of granite.

Obtaining a large volume of sand for further commercial purposes is not an easy task. First of all, you need to know all the nuances of production technology and the characteristics of the extracted sand. This problem can be solved if there is extra finance, since it is possible to hire specially trained personnel.

The financial aspect is another problem that you may encounter right away when starting this business. To put a business on stream and start making a profit, you need considerable investments and quite a lot of time.

Like any other business, the extraction of material is subject to taxation and registration in the state register. For this type of activity, it is best to form an LLC - a limited liability company. You can entrust the preparation of documentation and bringing it into proper form to special companies that do this for a fee. If time permits, then you can bypass all the authorities to collect certificates yourself. After completing a number of documents, you need to decide on the form of taxation.

To successfully open and develop your own quarry, you need registration of ownership and use of this deposit, a license. It is issued for a period of five years and can be extended in the future if the entrepreneur wishes.

The entire process of extracting minerals from a deposit is regulated by current legislation. Specifically in this case, the state standard 8736-93 “Construction sand” and TU 4417-75 “Quartz sand intended for welding work” apply.

Extraction technology

There are many ways to extract layers of sand from a quarry. All methods are divided into open and closed methods. How sand is extracted depends on the origin of the building material and the characteristics of the product being produced.

Open pit mining

The open method is the most common due to its availability. It is easier to get to deposits in the depths and on the surface. In addition, a minimum amount of construction equipment is used.

To begin with, stripping work is carried out on site. This is done using a bulldozer and scraper. If the work is not carried out, sand may be mixed with impurities, which is completely undesirable. At this time, experts determine the stripping ratio - the ratio of the base material and other minerals in the total volume.

Then trenches are made for working benches and transport routes for equipment. The angle of inclination of the ledge is individual for each area, since it is determined based on technical characteristics construction equipment.

Despite the fact that this method is quite simple to implement, it has its drawbacks. These include the low quality of the extracted products - they are often orange or yellow in color, which indicates their low quality.

Cleaning the sand from impurities helps improve the performance of open-pit mined minerals. The finished product can be used in plastering and masonry mortars.

Closed method

Such extraction is otherwise called the hydromechanical method. Since in Latin “hydro” means the presence of water, you can guess that this method is used if you need to get sand from the bottom of a reservoir.

To successfully develop mineral deposits under water, floating systems or special earthen shells are used.

Pontoons are used for a reason - they serve to securely secure cables and anchors. A powerful earth pump and a mechanized ripper are lowered to the bottom of the water column. The hydraulic mixture is sucked through the pipe and flows through special conductors into the hydraulic dumps. A mixture of water and sand is otherwise called pulp.

It is in hydraulic dumps that the sand is washed from the water, which flows back into the source. At this stage, the sand itself is cleaned of clay and other possible impurities.

The main tasks when developing a sand quarry

The goal of any business is to sell the extracted sand and make a profit. Extraction involves the sale of raw materials in the future. Its importance cannot be overestimated, which means that with properly established contacts and sales channels, it is necessary to determine the initial volumes and expected profit.

There may be several channels for selling a product. These can also be small wholesale stores selling construction sand, and large companies that will purchase material for their own needs.

Despite the fact that there are many ways to sell a product, to begin with you should not be focused only on money. First, it is important to decide on the starting price and supplies. It is most profitable to start sales closer to the place of production - this will reduce the time and cost of transportation to a minimum.

The main tasks after quarry development include:

• pricing;
• establishing contacts for product sales;
• purchase necessary equipment. Any sand mining activity cannot be done without an excavator, front-end loader, or dump truck.
• purchasing small household items. These include a fire shield, a drinking tank, an electricity generator, a change house and equipment for it, and walkie-talkies for workers.

Methods for extracting sea and river sand

Depending on the type of deposits and the type of construction sand produced, the material is divided into:

• nautical;
• river;
• alluvial;
• lake;
• deluvial.

The most common methods of extracting and developing soil are the processing of quarries, rivers and seas. River sand is extracted hydromechanically from the bottom of rivers and riverbeds that have dried up due to natural disasters.

If the deposit is located at a considerable distance from the storage site, then the extracted raw materials are placed on a barge and then delivered to the site. It also happens that the layer of sand at the bottom of the river is very large. Then dredgers and draglines are used.

One of the advanced methods of extracting from the bottom of the river is to drain part of the riverbed and use centrifugal separators. During operation, the machine separates sand particles and impurities, thereby improving the quality of the extracted raw materials. By washing the sand is made even cleaner, and after it dries the material can already be used.

Video: Sand mining

Preface

Identification of new mineral reserves is the most important national economic task in any country. At the dawn of socialism in Russia, attempts were made to solve this problem not only by specialist geologists, but also by broad sections of the population. A large and honorable role in its solution belonged to young people - Komsomol members, schoolchildren, young workers and collective farmers. And such a contribution was made by them.

Now the vast expanses of our huge planet still conceal a lot of undiscovered minerals and minerals. Finding them can not only be beneficial, but also bring pleasure, and knowledge in this area will allow you to broaden your horizons and learn more about the fascinating world of minerals of your homeland, the Earth.

Searching for and exploring mineral resources is not only important, but also exciting. In fact, what could be more interesting and exciting than organized summer hikes around your native land with the aim of studying and identifying its natural mineral wealth?! These riches lie not only in deposits of gold, diamonds and other similar valuable minerals. Mineral wealth may lie, for example, in the most ordinary clays, familiar to everyone.

Clays are important and necessary for many industries National economy minerals. For example, a type of clay, kaolin, serves as the main raw material for the porcelain, earthenware and paper industries. Refractory clays are used to make refractory products. Molding clays are used in foundries. Brick clays serve as the main raw material for brick production. Large-scale industrial and residential construction requires huge quantities of brick clay to produce bricks.

This story about clay contains instructions for young explorers of the subsoil and adult seekers of good adventures - about the meaning various types clays for our national economy and about the most simple ways searching for their deposits.

What is clay?

Clay is a widespread rock. Clay is a rock that is very complex and variable both in the composition of its minerals and in its physical and technological properties. The conditions for the formation of clays are extremely diverse.

Geological science has reliably established that pure clays, that is, not contaminated with various impurities, are rocks consisting of very small particles (about 0.01 mm or less), and these particles belong to certain minerals. Many researchers call them “clay” minerals. These minerals are complex chemical compounds containing aluminum, silicon and water. In mineralogy they are called hydrous aluminosilicates.

Clays have the ability to soak, dissolve in water into individual particles, forming, depending on the amount of water, either a plastic dough or a “suspension” (dregs), i.e., liquid mixtures in which the smallest particles of clay are suspended. Such clay suspensions have a pronounced viscosity.

Therefore, clay can be defined as an earthy rock consisting mainly of hydrous aluminosilicates with a particle size of less than 0.01 mm, easily dissolving in water, forming viscous suspensions or plastic dough, retaining its shape after drying and acquiring the hardness of stone after firing. .

How clay is formed

To understand the origin of clays, we must at least briefly dwell on the question of the origin of rocks in general. The earth's crust is made up of rocks formed at different times and under different conditions. The primary ones are “igneous” rocks (deep and eruptive), which are solidified magma.

Magma is a molten mass of minerals found within the earth. It can solidify near the surface without breaking through the earth's crust; in cavities with low pressure, forming deep rocks (granite, aplite, gabbro, etc.), and also come to the surface in the form of lava, as happens during volcanic eruptions. In the latter case, igneous rocks are called eruptive (diabase, basalt, trachyte, etc.).

During their long geological life, these primary rocks are exposed to the diverse forces of nature, which transform them into new rocks that are sharply different from the parent rocks. If such processing occurs on the surface of the earth or “in the immediate vicinity of it, new sedimentary rocks arise (sands, clays, limestones, gypsum, etc.). If they are processed in the deep parts of the earth’s interior at high temperatures and high pressures, metamorphic rocks are formed rocks (gneisses, schists, quartzites, etc.).

Not only igneous, but also metamorphic rocks can serve as material for the formation of sedimentary rocks, if for some reason they protrude to the surface. At the same time, metamorphic rocks can arise from sedimentary rocks if the latter are buried to great depths and are under pressure from overlying rocks. These three types of rocks - igneous, sedimentary and metamorphic - form the entire solid shell of our Earth - its lithosphere.

Clays are classified as sedimentary rocks. The formation of clays, like other sedimentary rocks, is associated with two processes: the chemical decomposition of the original (parent) rocks and their physical destruction. In nature, these processes do not occur separately, but together. The forces that break down solid rocks and transform them into loose sedimentary rocks are collectively known as weathering.

There are three types of weathering: physical, chemical and organic. Physical weathering is the mechanical destruction (crushing) of rocks without changes in their chemical and mineral composition.

Heat and cold are the main forces of physical weathering. As you know, the sun sends colossal thermal energy to the earth. During the day, the sun's rays heat the surface of the earth, and at night it cools. The fluctuation between day and night temperatures in some places on the globe reaches 40-50°. Temperature changes lead to cracking of rocks and their gradual destruction, which is facilitated by water and wind. Penetrating into cracks and freezing there, water acts like a wedge - it breaks off huge blocks of stone, which roll down to the foot of the mountains and form huge screes around them. Large fragments, under the influence of the same forces - temperature, water and wind - are subject to further destruction, eventually turning into the smallest sand and the finest dust, carried away by water into sea basins.

Chemical weathering is the decomposition of rocks with the formation of new chemical and mineral substances. The intensity of the chemical weathering process is directly dependent not only on the mineral composition of the decomposing rock and external conditions, but also on the degree of its mechanical destruction. Chemical reactions occur faster, easier and more completely with small particle sizes. Along with this, chemical decomposition itself accelerates the process of mechanical destruction.

Chemical weathering is caused by gases (and primarily atmospheric air), water and salts dissolved in it. Penetrating through cracks into rocks, water, saturated with oxygen, carbon dioxide and other substances, decomposes the minerals it encounters along the way, dissolves and carries away some chemical elements and deposits others in rocks.

Organic weathering is the destruction of rocks as a result of the vital activity of plants and animal organisms. By penetrating cracks with their roots, plants split rocks into pieces. At the same time, plant roots, releasing acids and, when rotting, carbon dioxide, destroy rocks chemically. Huge colonies of microorganisms covering the surface of rocks in the form of lichens, as well as countless bacteria inhabiting the soil and bottom of reservoirs, in turn, tirelessly destroy and modify rocks.

Thus, extremely complex and lengthy processes of processing some minerals into others take place on the surface of the earth and near it. It is as a result of these processes of destruction of primary hard rocks and processing of minerals that clays are formed.

Of the “clay” minerals, kaolinite is the most studied. It is a compound of silicon oxide, aluminum oxide and water. When viewed under a microscope, its crystals have the form of small plates or scales. Kaolinite is formed as a result of surface chemical weathering in an acidic environment of both igneous and metamorphic and sedimentary rocks containing predominantly mica and feldspar. Especially pure kaolin clays are formed during the chemical weathering of granites, pegmatites, aplites, etc. Kaolinite is composed of clays of a very valuable white variety - kaolin and some refractory clays.

Another clay mineral is halloysite. Its chemical composition is close to kaolinite, but contains slightly more water. When viewed under a microscope, its crystals have the shape of needles. It often contains an admixture of iron. It is formed mainly under alkaline and neutral conditions. The source rocks are usually gabbro, diabase, etc.

Finally, a typical clay mineral is montmorillonite, a very common mineral in soils and many marine clays. Especially pure montmorillonite clays, used in the oil industry (for oil refining), are formed as a result of the chemical decomposition of products of volcanic activity: ashes, lavas, tuffs, etc. When examined under a microscope, this mineral turns out to be composed of extremely small scales, leaves and fibrous secretions. Its peculiarity is the ability to “swell” greatly under the influence of water.

Depending on the methods of formation, the nature and form of occurrence of clays vary.

Clay deposits, formed mainly as a result of chemical weathering (“residual” deposits), usually have a mantle-like form of occurrence, differ high power(up to 100 m or more) and spread over large areas.

Kaolinite is the most characteristic mineral for these deposits. It makes up from 10-20 to 100% of such “residual” deposits. Clay deposits that arose as a result of erosion, transfer and secondary deposition of clay particles from residual deposits are characterized by pronounced layering, relatively small thickness and diversity of the chemical composition of individual layers. The area of ​​distribution of these deposits can vary widely.

Properties of clays

The properties of clays depend entirely on their chemical and mineral composition, as well as on the size of their constituent particles. Already these alone. facts point us to the most important properties clay

The most important properties of clays are:

• the ability to form thin “suspensions” (cloudy puddles) and viscous dough when mixed with water;
• ability to swell in water;
• the plasticity of clay dough, i.e. its ability to take and retain any shape in its raw form;
• the ability to maintain this shape even after drying with a decrease in volume;
• stickiness;
• binding ability;
• water resistance, i.e. the ability, after saturation with a certain amount of water, not to allow water to pass through.

Various products are made from clay dough - jugs, krinks, pots, bowls, etc., which after firing become completely hard and do not allow water to pass through. Brick factories produce construction bricks from clay, which also have great mechanical strength. This indicates another important property of clay - its ability to harden after firing, giving a material that does not soak in water and is impermeable to it.

Clays can be of all colors - from white to black. In Ukraine and some other regions of the USSR, white clay serves as a material for whitewashing walls, stoves, etc. When they want to paint walls in colored tones, they use yellow, red, green and other clays. Thus, here we are dealing with a new property of clay - its coloring and covering ability.

Oil refineries use certain types of clays to purify petroleum products. They are also used to purify vegetable oils and fats. Thus, we are faced with another property of clay: its ability to absorb from the liquid some substances dissolved in it. In technology, this property is called “sorption capacity.”

Due to the fact that clays contain a large amount of aluminum oxide, they are also used as chemical raw materials, mainly for the production of sulfate salts of this metal.

These are the most important properties of clays, on which numerous types of their practical uses are based. Of course, not all clays have the listed properties and not to the same extent.

Types of clays

The most valuable types of clay for the national economy are:

Kaolin is a white clay. It is mainly composed of the mineral kaolinite. Typically less plastic than other white clays. It is the main raw material for the porcelain, earthenware and paper industries.

Refractory clays. These clays are characterized by a white and gray-white color, sometimes with a slightly yellowish tint. When fired, they must withstand temperatures of at least 1580° without softening. The main minerals that form them are kaolinite and hydromicas. Their plasticity may vary. These clays are used for the production of fireproof and porcelain and earthenware products.

Acid-resistant clays. These clays are a type of fire clay with small amounts of iron, magnesium, calcium and sulfur. Used for chemical porcelain and earthenware products.

Molding clays- a type of refractory clay with increased plasticity and increased binding ability. They are used as a binding material in the manufacture of molds for metallurgical casting. Sometimes refractory clays (less stable when fired than refractory clays) and even low-melting clays—bentonite clays—are also used for these purposes.

Cement clays They have different colors and different mineral compositions. Magnesium is a harmful impurity. These clays are used to produce Portland cement.

Brick clays- fusible, usually with a significant admixture of quartz sand. Their mineral composition and color may vary. These clays are used to make bricks.

Bentonite clays. The main mineral that forms them is montmorillonite. Their color is different. They swell greatly in water. They have a higher bleaching power than other clays. These clays are used for purifying petroleum products, vegetable and lubricating oils, when drilling wells, and sometimes, as noted earlier, in the manufacture of foundry molds.

In industry and technology, other types of clays are often called: pottery, tile, fulling, ceramic, drilling, earthenware, porcelain, capsule, construction, paint, etc. However, these names practically do not characterize the special properties of clays.

In production practice, there is also a division of clays into “fat” and “lean” (sandy loam, loam). This division of clays is associated with the degree of contamination with quartz sand. Quartz sand is the most common and almost always predominant impurity in clays, especially in residual clay deposits. In “fat” clays there is little sand, but in “lean” clays there is a lot of it.

As already indicated, clays are widespread in nature and usually occur at shallow depths from the surface. All this makes them a cheap type of mineral raw material. However, transporting them over long distances is impractical. Therefore, they try to use them locally as mineral raw materials whenever possible. For example, all brick and tile factories are necessarily built on the clay deposit itself, since it is much more expedient to transport more expensive fuel to the factory than huge masses of wet and very heavy clay.

However, not all types of clay are found everywhere. Some varieties of them occur only in certain, few areas. Meanwhile, the demand for them is very high, and consumers (factories, construction sites, etc.) are often many hundreds and even thousands of kilometers away from the production site. In such cases, long-distance transportation of clay becomes inevitable.

The most rare clays include, first of all, high-grade bentonite clays and all varieties of white clays - kaolin, porcelain, earthenware, refractory, molding and acid-resistant. It is in the search for these rare varieties of clays that the greatest attention should be paid.

Voluntary subsoil prospectors can and should provide the state with serious assistance in identifying such valuable varieties of clays. The white color of clays makes them extremely easy to find. Layers of white clay are visible in outcrops along river banks and in ravines.

However, it must be borne in mind that not only clays have a white color, but also a number of other rocks, in particular, pure quartz sands and especially chalk. In some places, the population calls chalk “clay,” although it has nothing in common with clay either in its chemical composition or in its properties. When mixed with water, chalk, like clay, smears well and may even seem plastic, but it is enough to drop a drop of hydrochloric acid on it, and it immediately reveals its chemical nature: the acid will begin to boil, as it were, from the release of carbon dioxide. This reaction of the rock to hydrochloric acid indicates that it is chalk and not clay.

White quartz sand is even easier to distinguish from white clay. It is absolutely non-plastic and when dry it crumbles even with a light touch.

Application of clays

Clays are classified as mineral raw materials for mass consumption. They, as already noted, are used in a wide variety of sectors of the national economy, for a variety of purposes. The following areas of industrial use of clays are of greatest economic importance:

Ceramics

Ceramics is one of the most ancient forms of human development mineral nature. Scientists have found that the most ancient ceramic products made from Nile silt date back to the 20th century BC, in other words, they are over 13,000 years old. On the European continent, dishes from an even earlier time have been discovered, made by Ice Age man, dating back over 15,000 years.

The Egyptians and Assyrians possessed extremely high ceramic production techniques. In particular, they knew how to cover their ceramics with colored glazes. The ancient Greeks and Romans achieved particular perfection in ceramics, as evidenced by the Greek black-figure and red-figure vases, remarkable for the beauty of their forms and subtle artistic taste.

The peoples of Asia also achieved remarkable success in ceramics. It is enough to point out the production of the finest porcelain tableware, which began in China about 4000 years ago.

In Russia, artistic ceramics has its own rich history. During excavations near Kerch, clay vessels and figurines dating back to the 4th-6th centuries AD were found. In the Middle Ages, ceramics became the favorite decorative material of the builders of ancient Russian cathedrals in Vladimir, Suzdal, Novgorod, etc. Wonderful examples of artistic tiles dating back to approximately the 15th and 16th centuries can still be seen in St. Basil's Cathedrals in Moscow. Kolomenskoye near Moscow.

In Pavlovsky, Kuskovsky, Ostankino and other palace-museums of Moscow, Leningrad and other cities, collections of works of Russian national ceramics, amazing in their beauty and originality, created by the talented hands of serf artists, have been preserved. Great achievements in the development of Russian artistic ceramics belong to Lomonosov’s contemporary, the prominent scientist D.I. Vinogradov, who created Russian porcelain.

Simultaneously with the development of porcelain production and artistic ceramics, the production of other types of ceramic products and, above all, building materials developed: bricks and tiles, refractory supplies, dishes, etc. The modern ceramic industry of the USSR is an advanced large-scale machine production. It unites a large number of factories and plants that produce products for various technical purposes.

Currently, not only clays are used as raw materials for the production of ceramic products, but also rocks such as talc, pyrophyllite, magnesite, dolomite, corundum, diaspore, kyanite, etc. However, clays continue to occupy first place among them.

The largest and most important branches of the ceramic industry for the national economy are the following:

The production of refractory supplies (bricks, beams, crucibles, etc.) plays an extremely important role in the national economy. Refractories are especially needed in ferrous and non-ferrous metallurgy, cement production, glass, fine ceramics and chemical industries. Fireproof are those products that can withstand temperatures of 1580° or more without softening. Refractory bricks are used mainly for lining furnaces in which heat treatment of certain materials is carried out.

Refractory clay products, depending on the source raw material and the content of aluminum oxide (alumina) in them, are divided into fireclay and semi-acid.

Fireclay are products that are made from a mixture of raw refractory clay and chamotte, which is also refractory clay, but pre-fired and ground into powder. Alumina in fireclay products must contain at least 30%.

Fireclay is a “leaning” additive, i.e., an additive that reduces the ductility and shrinkage of the product, which is inevitable during the process of drying and firing.

Semi-acid products contain less than 30% alumina and more than 65% silica (silicon oxide); they are also made from fireclay and refractory clay, but with the addition of quartz material.

Thus, the main raw material for the production of fireclay and semi-acid refractories is refractory clay, which can withstand temperatures of at least 1580°. Sometimes kaolin is also used as such a raw material.

Harmful impurities that reduce the fire resistance of clays are iron oxides, the content of which should not exceed 3.5%, and minerals with the presence of alkali (mica, feldspar), the content of which in clay should not exceed 2%. Lime is also harmful; it is allowed in quantities of no more than 1-1.5%.

Porcelain and earthenware production (fine ceramics) is the second major consumer of ceramic clays. Products made of porcelain and earthenware are distinguished from other ceramic products by their white shards. The difference between porcelain and earthenware lies in the degree of porosity of the shard: the porosity of earthenware is from 10 to 14%, while the porosity of porcelain does not exceed 0.5%.

The main raw material for fine ceramics is kaolin. Quartz or quartz sand is introduced into porcelain-faience masses as a thinning additive, and feldspar is added as a flux that lowers the firing temperature; The binding material is light-burning refractory plastic clay. Since these clays usually reduce the whiteness and translucency of porcelain, they try to add them in minimal quantities. This is only possible if the clay used has a high binding capacity.

Porcelain and earthenware products are fired at a temperature of 1350°. It is very important that in kaolin and in other minerals - components of porcelain and earthenware masses - there is as little iron as possible, the admixture of which not only reduces the overall whiteness of the shard, but also forms black spots and dots (“flies”) on it, significantly depreciating products. The content of iron compounds in clays used in the production of art porcelain should not exceed 0.5-0.9%.

Brick production is the largest consumer of clays. It does not impose particularly strict requirements on raw materials. To produce ordinary building bricks, widely used fusible sandy (“lean”) clays of any color are used. Deposits of such clays are found almost everywhere and a large number of local brick factories are based on them.

In addition to “lean” clays, brick production can also use “fat” plastic clays, but in this case quartz sand is added to give the bricks stability during drying and firing. Brick clays should not contain crushed stone, pebbles, gravel, large pieces of limestone, gypsum and other impurities. Building bricks are fired at a temperature of 900-1000°.

Along with small brick factories serving small consumers, powerful, fully mechanized enterprises are being created in our country near large industrial centers and large new buildings, producing many millions of bricks annually. Such enterprises require powerful raw material bases, the preparation of which is the most important national economic task.

The production of “stone goods” includes the manufacture of sewer pipes, wall and floor tiles, chemical glassware, etc. These products are characterized by dense sintered colored shards. In this production, fine-grained plastic refractory and refractory clays of various colors are used.

Pottery (jugs, jars, bowls, pots, etc.) is mainly produced in a makeshift way, manually. To make it, ferruginous, not very fatty, predominantly fine-grained clays are used.

Cement production

Portland cement is a finely ground powder obtained from a mixture of clay and limestone fired at a temperature of 1450-1500° (with a small addition of gypsum). This burnt mixture is called “clinker” in technology. Clinker can be prepared either from marl, which is a natural mixture of limestone and clay, or from an artificial mixture of them in approximately the ratio of 1 part clay and 3 parts limestone.

The quality requirements for clays used in the Portland cement industry are not particularly stringent. Widespread sandy brown and red clays are quite suitable, even with a very high iron content (up to 8-10%). The harmful impurity is magnesium oxide. The presence of coarse sand, pebbles, crushed stone and other large parts is not allowed. The possibility of using one or another type of clay largely depends on the chemical composition of the limestone mixed with it and is determined in almost every specific case.

Clay cement is a powder obtained by jointly grinding baked clay at a temperature of 750-900°, dry slaked lime and gypsum in a ratio of 80: 20: 2.

Preparation of casting molds

Casting of products from ferrous and non-ferrous metals is carried out in special molds. These forms are prepared from mixtures using quartz sand and clay as materials. Clay plays the role of a binding material, since quartz sand alone, lacking plasticity and binding ability, does not produce durable forms. The main technical requirement for foundry clays is their high binding capacity. In other words, they should be “fat”. In addition, the clay should not cause the mixture to burn to the surface of the castings.

Depending on the metal being smelted, the size and shape of the castings, clays of different mineral and chemical compositions are used. Preferred are “fat” clays with the smallest possible particle size, sufficiently fire-resistant, and with a high content of aluminum oxide. IN last years Bentonite clays, which have an exceptionally high binding ability, began to be successfully used in foundry. Although they are not fireproof and, moreover, even belong to the fusible type, their increased binding ability completely compensates for this deficiency. It allows them to be introduced into the molding mixture in an amount approximately four to five times less than conventional refractory clays. And this contributes to better gas permeability of the mold and reduces burning. Harmful impurities in molding clays include feldspar, mica, limestone, and minerals containing sulfur. They reduce the fire resistance of clay and increase burning.

Drilling of the wells

In recent years, clays have become widely used in drilling exploration and production wells. Mineral exploration by rotary drilling with the removal of samples of drilled rocks has become very widespread. Rotary drilling is carried out using special machines. The drill assembly consists of metal hollow rods, a core pipe and a drill bit, tightly attached to each other. As the well deepens, the rod grows larger. At its upper end it is attached to a machine driven by a special motor.

When drilling wells from rocks, cylindrical columns called cores are drilled using a crown. The drilled core is pushed inside the core pipe as the crown deepens. To extract the core, the projectile is raised to the surface from time to time. By stacking the cores in the order in which they were extracted, an accurate picture of the composition, structure, location and thickness of the drilled rocks is obtained.

For successful operation of the drilling rig, a clay solution is injected into the well. This solution is pumped into the well through a rod using a special pump. Jets of solution, circulating through the well, capture small particles of rock destroyed by the crown and carry them out. The clay solution also performs other extremely important functions, namely: a) forms a thin water-impermeable film on the walls of the well, preventing the penetration of liquid through pores and cracks into the surrounding rocks; b) strengthens the walls and thereby protects them from collapses; c) prevents the possibility of gas emissions from the well and the penetration of groundwater into them. In addition, the clay solution cools the drill bit, which becomes very hot when rotating.

Drilling equipment imposes its own specific requirements on clays. They must be very fine-grained, highly flexible and free of sand, gypsum, limestone and salts. Bentonite clays are most suitable for use in drilling. However, other types of clays may be quite suitable for these purposes. Clays that produce viscous solutions with a daily sediment of no more than 1% and the presence of sand of no more than 3-4% are quite suitable for the preparation of drilling fluids.

Purification of petroleum products, organic oils and fats

Some clays have a high adsorption capacity and are used for decolorization (bleaching) of various mineral and organic substances (kerosene, gasoline, vegetable oils, animal fats, fruit juices, etc.). They absorb various contaminants, mucus, resin, pigments, etc. Clays consisting primarily of the mineral montmorillonite (bentonite and so-called subbentonite) are suitable for this purpose. Some of them whiten well without any pre-treatment, others need it and are treated with sulfuric acid. The suitability of clay for bleaching is usually determined experimentally, since its bleaching ability depends not only on the nature of the clay itself, but also on the conditions under which the cleaning is carried out, and on the material composition of the material being bleached.

Paper industry

This industry uses a white type of clay - kaolin. It consumes up to 35% of all kaolin production. It is introduced into paper pulp as a filler in order to enhance the whiteness of the paper and make it denser and smoother. The smallest particles of kaolin, filling the gaps between the wood fibers from which paper pulp is produced, dramatically improve the quality of paper.

The main requirements of the paper industry for kaolin are white color and the absence of large grains of quartz sand. Large grains spoil not only the paper, but also the expensive units on which it is produced.

Rubber industry

This industry also uses kaolin as a filler. Its introduction into rubber increases mechanical properties rubber. For the production of rubber products, it is important that the kaolin particles are of the smallest size and that there are no large grains of quartz sand in it. Among the harmful impurities for this production are iron, sulfur, copper and manganese. The moisture content in kaolin in this case should not exceed 0.5%.

Paint production

This branch of production uses fine-grained ferruginous clays, from which yellow, brown and red paints are produced. The well-known ocher, mummy and umber are prepared from such clays. The main requirements of paint production are their uniformity, fine grain, purity and color intensity. In addition, the clay must have good covering power.

Chemical industry

Among many other important products, the chemical industry produces aluminum sulfate for water purification. Its production involves boiling clay, calcined at a temperature of 650° and crushed to 2 mm, with sulfuric acid. For the production of aluminum sulfate, “fat” clays with a minimum sand content are most suitable. The color of the clay does not matter in this case. The chemical industry also uses kaolin to make ultramarine paint.

Aluminum industry

This industry uses a type of clay - kaolin - to produce some aluminum alloys. In the future, in this industry, along with kaolin, other white clays will undoubtedly be widely used. At present, effective methods have already been developed for producing pure alumina from low-iron clays, suitable for the production of metallic aluminum.

Art

Plastic green, gray-green and gray clays are widely used in sculpture. Typically, all sculptors initially create their works from clay and then cast them in plaster or bronze. Only in rare cases is the clay original subjected to firing. A fired, unglazed clay sculpture is called “terracotta”; a glazed one is called “majolica”.

Other small consumers

There are many more industries that use clays. These include, for example, soap, perfume, textile, abrasive, pencil and a number of others.

Clays, in addition, are widely used in everyday life, especially in agriculture: for laying furnaces, claying currents, whitewashing walls, etc. The use of swelling clays of the bentonite type in the construction of dams, reservoirs and other similar structures has great prospects.

Improving the quality of clays

There are a number of clay deposits that are not being developed because the quality of the clay does not meet the requirements of the consuming sectors of the national economy. For example, kaolins from many deposits are unsuitable for most industries due to the high content of quartz sand or coloring oxides (iron and titanium). There are many refractory clays, the use of which in industry is impossible due to the admixture of minerals that lower their softening temperature.

White clays are in some cases spoiled by rusty spots and smudges, which reduce the overall whiteness of the material. Such stains and smudges are eliminated by manually selecting yellow pieces that go into the dump. Sometimes, to decolorize kaolin, it is washed in a weak solution of sulfuric acid. Clay is easily freed from sand by washing it with water in special machines and sedimentation devices. With such washing, larger and heavier grains of sand easily and quickly fall to the bottom of the nearest settling chambers, and the smallest light particles of clay matter slowly settle in special settling tanks.

There are other methods for enriching clays, but they are used much less frequently. To increase the bleaching ability of clays, they are treated (activated) with sulfuric acid, and to give colorful clays the desired shades, they are sometimes subjected to special firing. In practice, clay enrichment is used relatively rarely - only when it comes to varieties that are rarely found in nature (for example, kaolins, highly refractory and bentonite clays).

Such mass and not very demanding industries as brick, tile, pottery, cement, etc. use clays in their natural form.

Where and how to look for clay

Before you start searching for clay, you need to know for what purposes it is intended, because each production, as we have seen, makes its own demands on clay.

If its future consumer is known, the task of searching is greatly simplified, since at the first stage one can be guided by purely external signs characteristic of clays for a given purpose. For example, white color is typical of kaolins, as well as earthenware, porcelain and refractory clays.

Having determined the search area, it is necessary first of all to interview local residents, who can provide very valuable information about the occurrence of clays in this area. Then external signs are used that indicate the presence of clay deposits. These signs are the following:

• swampiness of the area;
• an abundance of streams and springs along river banks and ravines;
• low groundwater level in wells.

All these signs are associated with the water resistance of clay. They indicate its occurrence near the surface.

The easiest way to detect clay deposits is by rock outcrops in cliffs and along river banks. Layers of deposited rocks can lie horizontally, but they can also be located at some angle to the horizon and even stand vertically. Geologists say about such layers that they are “put on their heads.” The position of individual layers in an outcrop depends on various reasons: the topography of the bottom of the reservoir in which sediments accumulated, faults that occurred after their accumulation, landslides that occur near the shores, etc.

It is usually difficult to distinguish clay from other rocks in an outcrop by appearance. The boundaries of individual layers are in most cases obscured by rain flows and screes. For a more reliable inspection of the outcrops, they are cleared. Then the boundaries of individual sediments, even with insignificant layer thickness, are revealed quite clearly.

Clay in cleared outcrops is easily recognized. It is enough to pinch off a small piece of rock and lightly knead it between your fingers (if there is insufficient moisture, moisten it with water), like clay, if it is what it is, it is easily detected by a number of characteristic features. It does not crumble into individual grains, as happens with sand. It sticks to the skin and, easily yielding to even weak hand pressure, takes and retains its given shape. The plasticity and pliability of clay sharply distinguish it from other sedimentary rocks, for example, from limestone or dolomite, layers of which are often found in outcrops.

If the clay layer is of sufficient thickness (about 1-3 m) and is covered on top by a not very thick layer of other rocks (2-4 m), then the deposit can undoubtedly be of practical interest. In this case, it is necessary to make a schematic sketch of the cleared outcrop (section) to scale. A schematic section shows not only clay layers, but also layers of all overlying rocks and a layer of underlying (underlying) rock. The sketch is provided with a serial number and symbols, which are assigned to individual breeds. At the same time, in the notebook that the subsoil explorer should have, the serial number of the sketch is noted, a brief description of section, the time and place of sketching are indicated.

The approximate text of the entry in the book is as follows: “Cut No. 4; May 25, 2008; right bank of the river SOSNOVKA, 300 m below the carriage near the village. Stepanovka and 0.5 km from the station. Ippolitovka. The height of the bank from the river level is 10 m, the thickness of the white clay layer is 0.5 m; The thickness of the covering rocks is 1.5 m.

Clay sampling

The color of the clays, the depth of their occurrence and the thickness of the layers determined at the outcrop site do not always allow us to assess their suitability for industrial use. An assessment of the suitability of clays for certain practical purposes can usually be given only as a result of studying their quality.

A fairly reliable and comprehensive study of the qualities of clays is carried out in laboratories using special instruments. For such studies, samples are needed that give a correct idea of ​​the mineral and chemical composition of clays, as well as the size of its particles throughout the entire thickness of the formation, from its upper to lower boundaries.

If only one layer of clay is found, and the clay is homogeneous in appearance, one general sample is taken. If there are several layers, as well as if the clay in each layer is heterogeneous (in color, degree of sandiness, etc.), a special sample is taken from each layer and each layer different from the others. Each sample is numbered. Sample numbers are also indicated on the sketch of the outcrops at the place where they were taken.

Sampling in outcrops is carried out using the so-called “furrow method,” which involves excavating a certain amount of rock across the formation. The selection technique is very simple. In a previously cleared area, through the entire layer from top to bottom, make two parallel cuts with a shovel or an ax, each about 20 cm deep, at a distance of 10 cm from each other. From the area marked in this way, with the same shovel or knife, pieces of clay are cut out without gaps in the shape of a tetrahedral or trihedral prism.

If the clay is homogeneous, all pieces taken from a given cleared area are mixed, and the sample is reduced to a weight of 2-3 kg. In case of heterogeneous clays and the presence of several layers, samples taken from individual layers are not mixed, but are reduced and packaged separately for each layer or layer. Packaging is done in small fabric bags or paper. All samples, as indicated, are numbered. Each bag or bag with a sample must include a note indicating the sample number, as well as the layer and place from which it was taken. The same information is entered in the notebook, but with a more detailed description of the place where the sample was taken.

During layer-by-layer sampling, the number of samples taken in each layer is noted on the outcrop sketches.

On-site testing of clays

For in-depth laboratory testing of clays, selected samples are sent either to the nearest geological department or to another research organization engaged in the study of mineral raw materials, and in particular clays. Here the mineral composition of the selected samples, their chemical composition and all the most important physical and technical properties of clays are studied.

But sending samples for scientifically qualified laboratory tests does not exclude the possibility of a preliminary assessment of some properties of clays by the discoverers of the deposits themselves, including voluntary subsoil prospectors. For example, on site it is possible to approximately determine the degree of sandiness of clays. To do this, a certain pre-weighed amount of dried clay is soaked in a glass of clean water so that there is four times more water than clay. Then the sample in the glass is thoroughly mixed. After the clay has completely dissolved, the sample is allowed to stand for 10-15 minutes. During this time, sand, the grain size of which is much larger than the size of the clay particles, will settle to the bottom of the glass, and the clay particles will remain (in the form of turbidity) in suspension. After draining the liquid, the settled sand is dried and weighed. By dividing the weight of the sediment by the weight of the dry clay taken and multiplying the quotient of this division by 100, the percentage of sand content in the clay is obtained.

Without much difficulty it is possible to distinguish bentonite clays from kaolinite clays on site. To do this, a small piece of the test sample is immersed in water (on a saucer). Kaolinite clay will soon completely dissolve, forming a small cone, and bentonite clay, without dissolving, will begin to quickly increase in volume, maintaining the original shape of the taken piece for a long time.

It is also easy to determine the bleaching properties of clay yourself. To do this, a certain amount of it is dried (at a temperature of 120-200°) and then ground into the finest powder. This powder is poured into a bottle (necessarily white glass) and contaminated kerosene, gasoline, vegetable oil, etc., is poured into it in an amount approximately three times greater than the amount of clay taken. The mixture in the bottle is shaken for 10-15 minutes and then allowed to settle. After this, see how much the poured oil or kerosene brightens. The greater the lightening, the higher the bleaching properties of the clay.

It is very easy to determine the plasticity of clay on site. To do this, a small piece of clay is mixed with water until a well-formed dough is formed. Then roll out the resulting dough into a roller as thick as your index finger and 15-20 cm long and gradually bend this roller into a ring. Clays, which have high plasticity, bend into a ring easily and without the formation of cracks and breaks. It is impossible to obtain such a ring without cracks from thin, low-plasticity clays. The curvature of the arc before cracking serves as a measure of ductility.

Color also characterizes the quality of clay to a certain extent. White and light gray clays always contain little iron and are usually refractory or refractory. If their plasticity is low, a young mineral explorer can reasonably believe that he is dealing with kaolin. The red-yellow or red-brown color of the clay indicates that it is not fire-resistant and is only suitable for rough ceramics. The black color of the clay indicates a large admixture of organic substances in it. However, this still does not determine its technological properties. In some cases, such clays can turn out to be quite satisfactory ceramic raw materials, since after firing the organic impurities burn out and the color of the shard sometimes becomes almost white.

The presence of sand in clay can be easily determined by testing the clay. Clays that do not contain sand do not creak on the teeth. The more sand there is in the clay, the stronger it will be felt on the teeth.

First of all, it should be noted that in this article I am looking at clay that is suitable for modeling - a hobby that you like to devote a little time to. After all, what we're talking about is - where to get clay and, of course, for industrial scale production, clay mining is very different from mining to satisfy one’s own creative needs.

If you were preparing to open your own industrial line for the production of clay products, I would advise you to contact material suppliers, test the clay and enter into a supply agreement. Unless of course you own land plot, which is a notable and extensive source of this natural material..

For small-scale production and simple modeling, there are only two answers to the question of where to find clay: either in a store or in the ground.

The easiest way to prepare clay is to buy it. No, I’m not at all going to sell you clay, as it would be done on other materially interested resources, but I just want to say that a number of stationery stores sell powdered and ready-made clay, packaged in various packages. This is, most often, high-quality clay, ideal for learning the basics of modeling and the basics of sculpture. A kilogram of powdered clay is enough to master plastic arts.

If spending money on natural material somehow contradicts your principles, then the second method is ideal for such cases.

Where can you get clay?

If you look closely, red clay deposits can be found everywhere, at least in our middle zone.

• Places where preparations are made for construction work. Visit any construction site. The foundation pits have mountains of rock, and among them, most likely, there will be exposed clay deposits. This also includes:
  • road construction. By the way, when creating embankments, they try to get rid of clay, since it spoils any road surface;
  • places of communication (where trenches are dug - under a pipeline, for example);
  • quarries for the extraction of natural materials, even if they mine sand, there is a chance to find dumps of clay rocks and all that remains is to find a way to get to the protected site..
• Natural places where clay forms
  • at the dacha (if you dig deeper and in different places, there is a chance to stumble upon deposits);
  • on the banks of rivers and ravines you can find screes, where clay is visible among the layers of rock;
  • in places where water does not drain for a long time - a sure sign of the presence of clay.

The most important thing in finding clay is to choose the clay suitable for modeling based on its properties.

Determining the right clay is quite simple. Roll a small roller in your hand and try to bend it smoothly. The desired clay should not have cracks at the bend. If you still couldn’t find plastic clay, don’t despair - you can make something out of thin clay, you just have to be more careful and careful, omit some of the small details and make the shapes smoother. When fired, such clay exhibits less shrinkage and cracks, but the surface is rougher and less moisture resistant. For pottery production, the selection of clay is more strict and demanding.

If the quality of the clay does not suit you, you should give it the necessary properties by working magic on it using simple but labor-intensive methods, for example,

Clay is a fine-grained sedimentary rock, dust-like when dry, plastic when moistened.

Origin of clay.

Clay is a secondary product formed as a result of the destruction of rocks during the weathering process. The main source of clay formations are feldspars, the destruction of which under the influence of atmospheric agents forms silicates of the group of clay minerals. Some clays are formed by the local accumulation of these minerals, but most are sediments from water flows that accumulate at the bottom of lakes and seas.

In general, according to their origin and composition, all clays are divided into:

- sedimentary clays, formed as a result of the transfer to another place and deposition there of clayey and other products of the weathering crust. Based on their origin, sedimentary clays are divided into marine clays, deposited on the seabed, and continental clays, formed on the mainland.

Among marine clays there are:

• Coastal- are formed in coastal zones (turbulence zones) of seas, open bays, and river deltas. They are often characterized by unsorted material. They quickly change into sandy and coarse-grained varieties. Replaced by sandy and carbonate deposits along the strike. Such clays are usually interbedded with sandstones, siltstones, coal seams and carbonate rocks.
• Lagoon- are formed in sea lagoons, semi-enclosed with a high concentration of salts or desalinated. In the first case, the clays are heterogeneous in granulometric composition, insufficiently sorted and wind together with gypsum or salts. Clays from desalinated lagoons are usually finely dispersed, thin-layered, and contain inclusions of calcite, siderite, iron sulfides, etc. Among these clays there are fire-resistant varieties.
• Offshore- are formed at a depth of up to 200 m in the absence of currents. They are characterized by a uniform granulometric composition and large thickness (up to 100 m or more). Distributed over a large area.

Among the continental clays there are:

• Deluvial- characterized by a mixed granulometric composition, its sharp variability and irregular layering (sometimes absent).
• Ozernye with a uniform granulometric composition and finely dispersed. All clay minerals are present in such clays, but kaolinite and hydromicas, as well as minerals of hydrous oxides Fe and Al, predominate in clays of fresh lakes, and minerals of the montmorillonite group and carbonates predominate in clays of salt lakes. Belongs to lacustrine clays best varieties refractory clays.
• Proluvial, formed by temporary flows. Characterized by very poor sorting.
• River- developed in river terraces, especially in the floodplain. Usually poorly sorted. They quickly turn into sands and pebbles, most often non-stratified.

Residual - clays resulting from the weathering of various rocks on land, and in the sea as a result of changes in lavas, their ashes and tuffs. Down the section, residual clays gradually transform into parent rocks. The granulometric composition of residual clays is variable - from fine-grained varieties in the upper part of the deposit to uneven-grained ones in the lower part. Residual clays formed from acidic massive rocks are not plastic or have little plasticity; Clays formed during the destruction of sedimentary clay rocks are more plastic. Continental residual clays include kaolins and other eluvial clays. In the Russian Federation, in addition to modern ones, ancient residual clays are widespread - in the Urals, in the West. and Vost. Siberia (there are also many of them in Ukraine) - of great practical importance. In the mentioned areas, clays predominantly montmorillonite, nontronite, etc. appear on basic rocks, and on medium and acidic rocks - kaolins and hydromica clays. Marine residual clays form a group of bleaching clays composed of minerals of the montmorillonite group.

Clay is everywhere. Not in the sense - in every apartment and plate of borscht, but in every country. And if there are not enough diamonds, yellow metal or black gold in some places, then there is enough clay everywhere. Which, in general, is not surprising - clay, sedimentary rock, is a stone worn by time and external influences to the state of powder. The last stage of stone evolution. Stone-sand-clay. However, the last one? And sand can form into stone - golden and soft sandstone, and clay can become brick. Or a person. Who's got some luck?

The clay is colored by the creator stone and salts of iron, aluminum and similar minerals that happen to be nearby. Various organisms reproduce, live and die in clay. This is how red, yellow, blue, green, pink and other colored clays are obtained.

Previously, clay was mined along the banks of rivers and lakes. Or they dug a hole specifically for it. Then it became possible not to dig the clay yourself, but to buy it from a potter, for example. During our childhood, we dug out ordinary red clay ourselves, and bought noble white clay in artists’ stores or, especially pure clay, in a pharmacy. Now a nice little shop selling cosmetics will certainly have clay. True, not entirely in its pure form, but mixed with various detergents, moisturizers and nourishing agents.

Our land is rich in clay. Roads and paths cut into loamy soil become sources of dust in the heat, and in slush they become pure mud. Clay dust covered the traveler from head to toe and added to the housework of the housewives whose house stood by the road. Surprisingly, there was no less dust near roads covered with asphalt. True, he turned from red to black. Ledum, thickly mixed with clay, not only prevents a pedestrian from walking and a wheel from moving, but also, depending on the mood, you don’t mind swallowing a boot or a jeep.

Clay consists of one or more minerals of the kaolinite group (derived from the name of the locality Kaolin in the People's Republic of China (PRC)), montmorillonite, or other layered aluminosilicates (clay minerals), but may also contain sand and carbonate particles. As a rule, the rock-forming mineral in clay is kaolinite, its composition is: 47% silicon (IV) oxide (SiO 2), 39% aluminum oxide (Al 2 O 3) and 14% water (H 2 0). Al2O3 And SiO2- constitute a significant part of the chemical composition of clay-forming minerals.

The diameter of clay particles is less than 0.005 mm; Rocks consisting of larger particles are usually classified as loess. Most clays are gray in color, but there are clays in white, red, yellow, brown, blue, green, purple and even black. The color is due to impurities of ions - chromophores, mainly iron in valence 3 (red, yellow) or 2 (green, bluish).

Dry clay absorbs water well, but when wet it becomes waterproof. After kneading and mixing, it acquires the ability to take different shapes and retain them after drying. This property is called plasticity. In addition, clay has binding ability: with powdery solids(sand) gives a homogeneous “dough”, which also has plasticity, but to a lesser extent. Obviously, the more sand or water admixtures in the clay, the lower the plasticity of the mixture.

According to the nature of the clays, they are divided into “fat” and “lean”.

Clays with high plasticity are called “fat” because when soaked they give a tactile sensation of a fatty substance. “Fatty” clay is shiny and slippery to the touch (if you take such clay on your teeth, it slips), and contains few impurities. The dough made from it is soft. Bricks made from such clay crack when dried and fired, and to avoid this, so-called “lean” substances are added to the mix: sand, “lean” clay, burnt brick, pottery grit, sawdust and so on.

Clays with low plasticity or non-plasticity are called “lean”. They are rough to the touch, with a matte surface, and when rubbed with a finger, they easily crumble, separating earthy dust particles. “Skinny” clays contain a lot of impurities (they crunch on the teeth); when cut with a knife, they do not produce shavings. Bricks made from “lean” clay are fragile and crumbly.

An important property of clay is its relationship to firing and, in general, to elevated temperatures: if soaked clay in air hardens, dries and is easily wiped into powder without undergoing any internal changes, then at high temperatures chemical processes occur and the composition of the substance changes.

At very high temperatures, clay melts. The temperature of melting (beginning of melting) characterizes the fire resistance of clay, which is not the same for its different varieties. Rare types of clay require colossal heat for firing - up to 2000°C, which is difficult to obtain even in factory conditions. In this case, there is a need to reduce fire resistance. The melting temperature can be reduced by adding the following substances (up to 1% by weight): magnesia, iron oxide, lime. Such additives are called fluxes (fluxes).

The color of the clays is varied: light gray, bluish, yellow, white, reddish, brown with various shades.

Minerals contained in clays:

• Kaolinite (Al2O3 2SiO2 2H2O)
• Andalusite, disthene and sillimanite (Al2O3 SiO2)
• Halloysite (Al2O3 SiO2 H2O)
• Hydrargillite (Al2O3 3H2O)
• Diaspore (Al2O3 H2O)
• Corundum (Al2O3)
• Monothermite (0.20 Al2O3 2SiO2 1.5H2O)
• Montmorillonite (MgO Al2O3 3SiO2 1.5H2O)
• Muscovite (K2O Al2O3 6SiO2 2H2O)
• Narkite (Al2O3 SiO2 2H2O)
• Pyrophyllite (Al2O3 4SiO2 H2O)

Minerals contaminating clays and kaolins:

• Quartz(SiO2)
• gypsum (CaSO4 2H2O)
• dolomite (MgO CaO CO2)
• Calcite (CaO CO2)
• Glauconite (K2O Fe2O3 4SiO2 10H2O)
• Limonite (Fe2O3 3H2O)
• Magnetite (FeO Fe2O3)
• Marcasite (FeS2)
• Pyrite (FeS2)
• Rutile (TiO2)
• Serpentine (3MgO 2SiO2 2H2O)
• Siderite (FeO CO2)

Clay appeared on earth many thousands of years ago. Its “parents” are considered to be rock-forming minerals known in geology - kaolinites, spars, some varieties of mica, limestones and marbles. Under certain conditions, even some types of sand transform into clay. All known rocks that have geological outcrops on the surface of the earth are subject to the influence of the elements - rain, whirlwind storms, snow and flood waters.

Temperature changes day and night, heating of the rock sun rays promote the appearance of microcracks. Water gets into the cracks that form and, freezing, breaks the surface of the stone, forming a large amount of tiny dust on it. Natural cyclones crush and grind dust into even finer dust. Where the cyclone changes its direction or simply dies down, huge accumulations of rock particles form over time. They are pressed, soaked in water, and the result is clay.

Depending on what rock the clay is formed from and how it is formed, it acquires different colors. The most common clays are yellow, red, white, blue, green, dark brown and black. All colors, except black, brown and red, indicate the deep origin of the clay.

The colors of clay are determined by the presence of the following salts in it:

• red clay - potassium, iron;
• greenish clay - copper, ferrous iron;
• blue clay - cobalt, cadmium;
• dark brown and black clay - carbon, iron;
• yellow clay - sodium, ferric iron, sulfur and its salts.

Various colored clays.

We can also give an industrial classification of clays, which is based on the assessment of these clays based on a combination of a number of characteristics. For example, this appearance products, color, sintering (melting) interval, resistance of the product to sudden changes in temperature, as well as the strength of the product to impacts. Based on these characteristics, you can determine the name of the clay and its purpose:

• china clay
• earthenware clay
• white-burning clay
• brick and tile clay
• pipe clay
• clinker clay
• capsule clay
• terracotta clay

Practical use of clay.

Clays are widely used in industry (in the production of ceramic tiles, refractories, fine ceramics, porcelain-faience and sanitary ware), construction (production of bricks, expanded clay and other building materials), for household needs, in cosmetics and as a material for artistic works (modeling). Expanded clay gravel and sand produced from expanded clay by annealing with swelling are widely used in the production of building materials (expanded clay concrete, expanded clay concrete blocks, wall panels, etc.) and as a heat and sound insulating material. This is a lightweight porous building material obtained by firing low-melting clay. It has the shape of oval granules. It is also produced in the form of sand - expanded clay sand.

Depending on the clay processing mode, expanded clay of different bulk density (volume weight) is obtained - from 200 to 400 kg/M3 and higher. Expanded clay has high heat and noise insulation properties and is used primarily as a porous filler for lightweight concrete, which has no serious alternative. Expanded clay concrete walls are durable, have high sanitary and hygienic characteristics, and expanded clay concrete structures built more than 50 years ago are still in use today. Housing built from prefabricated expanded clay concrete is cheap, high quality and affordable. The largest producer of expanded clay is Russia.

Clay is the basis of pottery and brick production. When mixed with water, clay forms a dough-like plastic mass suitable for further processing. Depending on the place of origin, natural raw materials have significant differences. One can be used in its pure form, the other must be sifted and mixed to obtain a material suitable for the manufacture of various trade items.

Natural red clay.

In nature, this clay has a greenish-brown color, which is given to it by iron oxide (Fe2O3), which makes up 5-8% of the total mass. When fired, depending on the temperature or type of oven, the clay acquires a red or whitish color. It kneads easily and can withstand heating of no more than 1050-1100 C. The great elasticity of this type of raw material allows it to be used for working with clay plates or for modeling small sculptures.

White clay.

Its deposits are found all over the world. When wet, it is light gray, and after firing it becomes whitish or ivory. White clay is characterized by elasticity and translucency due to the absence of iron oxide in its composition.

Clay is used to make dishes, tiles, and plumbing items, or for crafts made from clay plates. Firing temperature: 1050-1150 °C. Before glazing, it is recommended to work in an oven at a temperature of 900-1000 °C. (Firing of unglazed porcelain is called bisque firing.)

Porous ceramic mass.

Clay for ceramics is a white mass with a moderate calcium content and high porosity. Its natural color ranges from pure white to greenish-brown. Burns when low temperatures. Unfired clay is recommended, as for some glazes a single firing is not sufficient.

Majolica is a type of raw material made from fusible clay with a high content of white alumina, fired at a low temperature and covered with a glaze containing tin.

The name "majolica" comes from the island of Mallorca, where it was first used by the sculptor Florentino Luca de la Robbia (1400-1481). Later this technique was widespread in Italy. Ceramic trade items made from majolica were also called earthenware, since their production began in workshops for the production of earthenware.

Stone ceramic mass.

The basis of these raw materials are fireclay, quartz, kaolin and feldspar. When wet it has a black-brown color, and after wet firing it has an ivory color. When applying glaze, stone ceramics are transformed into a durable, waterproof and fireproof product. It can be very thin, opaque or in the form of a homogeneous, densely sintered mass. Recommended firing temperature: 1100-1300 °C. If it is disturbed, the clay may crumble. The material is used in various technologies production of commercial pottery items from lamellar clay and for modeling. Trade items made of red clay and stone ceramics are distinguished depending on their technical properties.

Clay for porcelain trade objects consists of kaolin, quartz and feldspar. It does not contain iron oxide. When wet it has a light gray color, after firing it is white. Recommended firing temperature: 1300-1400 °C. This type of raw material is elastic. Working with it on a pottery wheel requires high technical costs, so it is better to use ready-made forms. This is a hard, non-porous clay (with low water absorption - Ed.). After firing, the porcelain becomes transparent. Glaze firing takes place at a temperature of 900-1000 °C.

Various porcelain trade items, molded and fired at 1400°C.

Large-pored, coarse-grained ceramic materials are used for the manufacture of large-sized commercial items in construction, small-form architecture, etc. These varieties can withstand high temperatures and thermal fluctuations. Their plasticity depends on the content of quartz and aluminum (silica and alumina - Ed.) in the rock. The overall structure contains a lot of alumina with a high chamotte content. The melting point ranges from 1440 to 1600 °C. The material sinteres well and shrinks slightly, so it is used to create large objects and large-format wall panels. When making artistic objects, the temperature should not exceed 1300°C.

This is a clay mass containing an oxide or colorful pigment, which is a homogeneous mixture. If, penetrating deep into the clay, part of the paint remains suspended, then the even tone of the raw material may be disrupted. Both colored and ordinary white or porous clay can be purchased in specialized stores.

Masses with colored pigment.

Pigments- these are inorganic compounds that color clay and glaze. Pigments can be divided into two groups: oxides and colorants. Oxides are a naturally occurring basic material that forms among the rocks of the earth's crust, is purified and atomized. The most commonly used are: copper oxide, which takes on a green color in the oxidizing firing environment; cobalt oxide, which produces blue tones; iron oxide, which gives blue tones when mixed with glaze, and earth tones when mixed with clay. Chromium oxide gives the clay an olive green color, magnesium oxide gives it brown and purple tones, and nickel oxide gives it a grayish-green color. All these oxides can be mixed with clay in a proportion of 0.5-6%. If their percentage is exceeded, the oxide will act as a flux, lowering the melting point of the clay. When painting trade items, the temperature should not exceed 1020 °C, otherwise firing will not produce results. The second group is dyes. They are obtained industrially or by mechanical processing of natural materials, which represent a full range of colors. Dyes are mixed with clay in a proportion of 5-20%, which determines the light or dark tone of the material. All specialized stores have an assortment of pigments and dyes for both clay and engobes.

Preparing ceramic mass requires a lot of attention. It can be composed in two ways, which give completely different results. A more logical and reliable way: add dyes under pressure. A simpler and, of course, less reliable method: mix dyes into the clay by hand. The second method is used if there is no exact idea about the final coloring results or there is a need to repeat certain colors.

Technical ceramics.

Technical ceramics - large group ceramic trade items and materials obtained by heat treatment of a mass of a given chemical composition from mineral raw materials and other high-quality raw materials that have the necessary strength and electrical properties (high volumetric and surface resistance, high electrical strength, small dielectric loss tangent).

Cement production.

To make cement, calcium carbonate and clay are first extracted from quarries. Calcium carbonate (approximately 75% of the quantity) is crushed and thoroughly mixed with clay (approximately 25% of the mixture). Dosing of starting materials is an extremely difficult process, since the lime content must correspond to the specified amount with an accuracy of 0.1%.

These ratios are defined in the specialized literature by the concepts of “calcareous”, “siliceous” and “alumina” modules. Since the chemical composition of the starting raw materials constantly fluctuates due to geological origin, it is easy to understand how difficult it is to maintain a constant modulus. In modern cement plants, computer control in combination with automatic analysis methods has proven itself well.

Properly composed sludge, prepared depending on the chosen technology (dry or wet method), is introduced into a rotary kiln (up to 200 m long and up to 2-7 m in diameter) and fired at a temperature of about 1450 °C - the so-called sintering temperature. At this temperature, the material begins to melt (sinter), it leaves the kiln in the form of more or less large lumps of clinker (sometimes called Portland cement clinker). Firing occurs.

As a result of these reactions, clinker materials are formed. After leaving the rotary kiln, the clinker enters the cooler, where it is sharply cooled from 1300 to 130 °C. After cooling, the clinker is crushed with a small addition of gypsum (maximum 6%). The size of cement grains ranges from 1 to 100 microns. It is better illustrated by the concept of “specific surface area”. If we sum up the surface area of ​​the grains in one gram of cement, then, depending on the grinding thickness of the cement, we get values ​​from 2000 to 5000 cm² (0.2-0.5 m²). The predominant part of cement in special containers is transported by road or rail. All overloads are performed pneumatically. A minority of cement products are delivered in moisture- and tear-resistant paper bags. Cement is stored at construction sites mainly in liquid and dry states.

Supporting Information.