Limestone is a natural stone of soft sedimentary rock of organic or organo-chemical origin. The main element that makes up limestone is calcium carbonate (calcite). In addition, limestone may also contain impurities of quartz, phosphate, silicon, clay, as well as sand particles, calcareous remains of microorganism skeletons.
Limestone formations
Limestone is formed mainly in shallow marine environments. However, there are cases where natural limestone was formed outside of normal conditions - in a freshwater environment. Stone deposits are composed of sediments and strata. Lime deposits are sometimes formed in the same way as salt and gypsum deposits - as a result of the evaporation of water from sea lagoons and lakes. But, despite this, the main localization of limestone deposits is in the seas, which are not characterized by intense drying.
The origin of limestone is mainly associated with the release of calcium carbonate by living organisms from sea water, which is necessary for the formation of skeletons and shells. The accumulation of these remains of dead organisms mainly occurs at the bottom of the seas. Coral reefs- one of the most bright examples how calcite is extracted and accumulated. Sometimes, if you break the limestone rock, you can see the presence of individual shells. Sea currents and sea waves have a destructive effect on reefs, as a result of which calcium carbonate is precipitated from the water at the bottom of the seas, which is added to lime debris. In addition, young limestone rocks are formed with the participation of calcite, which comes as a result of the destruction of ancient rocks.
Calcium carbonate, which is part of the rock, is able to dissolve in water, resulting in the formation of karst. There are also cases of its decomposition into base and carbon dioxide. However, this requires proper conditions, therefore, calcium carbonate decomposes exclusively at great depths, as a result of which, under the influence of the heat of the earth, gas is released for mineral waters.
Depending on the conditions of formation, limestone is divided into types. The most common is shell rock. Its formation involves fragments and many shells of marine animals. However, in addition to this type, there are others, among which are:
- Bryozoan limestone. Its main components are the remains of bryozoans, i.e. invertebrate animals that are quite small in size and live in colonies in the seas.
- Nummulite limestone. This type of stone contains extinct single-celled organisms called Nummulites, which belong to the order of Foraminifera.
- Marble-like limestone. This type is divided into two subtypes: thin-layered and massively layered. It is no secret that metamorphism causes the recrystallization of limestone, resulting in the formation of marble.
| Limestone structure | Hardness MPa | Yield strength MPa | Plasticity coefficient | Young's modulus E 10 -4, MPa | Specific contact work J/cm |
|---|---|---|---|---|---|
| Organogenic highly porous | - | 150-400 | - | 0,8 | 66 |
| Organogenic porous | 580-1150 | 350 | 7,0 | 2,0 | 23-38 |
| Organogenic dense | 1100-2000 | 500-1100 | 2,0-5,0 | 2,0-5,0 | 7-28 |
| Pelitomorphic highly porous | - | 100-250 | ∞ | 0,6-0,8 | 237 |
| Oolitic highly porous | - | 300-460 | ∞ | 1,7-2,8 | 170 |
| Pelitomorphic dense | 1200-2000 | 550-1150 | 2,0-6,0 | 1,5-5,0 | 7-25 |
| Fine-grained porous weathered | - | 180 | ∞ | - | 152 |
| Fine-grained dense | 1200-2000 | 300-1200 | 2,5-4,5 | 2,0-4,0 | 7-18 |
Thus, it is worth saying that limestone is a monomineral rock that, in addition to the main component, contains many different impurities. The name of limestone, as a rule, depends on the type of these impurities, as well as the structure, their geological age and the nature of occurrence: oolitic limestones, ferruginous limestones, flagstone limestones, Triassic limestones, etc.
Natural limestone is characterized by a light gray color, but despite this, it can also be black or white. Limestone with a bluish, pink or yellow tint is acceptable, depending on the impurities contained in the stone.
Limestone deposits
There is no shortage of limestone in the world, since it is a fairly common sedimentary rock formed with the participation of living organisms in the aquatic environment.
Entire alpine chains are formed from limestone. Limestones also took part in the formation of the Crimean mountains. However, these are not the only places in the world where the stone is found. Its deposits are known in the territory former USSR(Central Economic Region), in the territory North Caucasus, Volga region, Baltic states, Moldavian SSR, Azerbaijan SSR. Among the main lime deposits are:
- Afanasyevskoye field, located in the Moscow region. It is the main source of white limestone, which is used in the production of cement;
- Barsukovskoye field, which is located in the Tula region. Fluxed limestone is extracted from it;
- Guryevskoye (Venevskoye) field. It is also located in the Tula region and is a source of extraction of dense limestone, from which crushed stone is produced;
- Oknitskoye field (Moldavian SSR). Contains shell-oolitic limestone, used in the process of forming saw wall blocks;
- Badrak-Alminskoye field. Located in Crimea. It was there that deposits of white shell sawn limestone were discovered, which is the main material for the production of facing and wall materials;
- Shakhtakhtinskoye field (Azerbaijan SSR). It is a deposit of greyish-yellow and light brown saw-cut cavernous travertine limestone, from which facing slabs are produced;
- The Zhetybai deposit, located on the Mangishlak Peninsula, contains deposits of pink, light gray, gray-yellow porous shell sawn limestone, which is also used for the production of facing slabs.
| Field | Region | Reserves, thousand tons* | Area of use, quality | Degree of development |
|---|---|---|---|---|
| Pronsky | Ryazan region | 657980 | state reserve | |
| Sukhorechenskoe | Chelyabinsk region | 418330 | fluxing limestones; CaO - 50.5-55.2%; SiO2 - 0.24-3.04% | state reserve |
| Urusovskoe | Tula region | 415768 | fluxing limestones; CaO - 52-55.8%; SiO2 - 0.1-1%; MgO - 0.3-1% | state reserve |
| Galyanskoye | Sverdlovsk region. | 384244 | fluxing limestones; CaO - 55.3%; SiO2 - 0.15%; P - 0.013%; MgO - 0.51% | developed |
| Akkermanovskoe | Orenburg region | 376303 | fluxing limestones; CaO - 51.2-56%; SiO2 - 0.10-3.37% | developed |
| Dzhegutinskoe | Karachay-Cherkess Republic | 352269 | raw materials for cement production | developed |
|
Chanvinskoe (Kostanoksky section) |
Perm region | 333253 | limestones for chemical production(CaCO3 - 94.0%; MgCO3 - 4%; SiO2 - 2.5%) | developed |
| Karachkinskoe | Kemerovo region. | 322818 | fluxing limestones | developed |
| Pikalevskoe | Leningrad region. | 307278 | fluxing limestones; CaO - 53.6%; SiO2 - 0.9%; MgO - 1.4% | developed |
| Solominskoye | Kemerovo region. | 306129 | raw materials for cement production | developed |
| Malo-Salairskoe | Kemerovo region. | 275155 | fluxing limestones | developed |
| Khrapovitskoe | Vladimir region | 258555 | raw materials for cement production | state reserve |
| Podgornoye | Krasnoyarsk region | 248104 | fluxing limestones; CaO - 54.13%; SiO2 - 1.56%; P2O5 - 0.048% | state reserve |
Limestone mining
When extracting limestone, several methods are used to extract it from the bowels of the earth. These methods include:
- open career path. Considered the most common. At this method the top soil layer is removed and a quarry is formed, in which pyrotechnic work can be carried out, through which portions of limestone are crushed and detached. The next stage of this method is to transport the stone to the place of its processing. Mining vehicles are used for this process.
- explosive way. In this case, the deposits are opened by removing the earth from them with bulldozers. After this, clay and substandard limestone are also removed from them. In places where limestone is mined, wells are formed into which explosives are placed. If this process is properly organized, fairly large limestone layers are broken off, which are transported by dump trucks for further processing.
- mining with a milling machine. This method mechanically converts the rock into crumbs. Thus, several processes are carried out simultaneously - crushing, loading and transportation.
It is worth noting that after extracting the limestone, the quarry should be filled with soil and also planted with herbs and plants. Typically, these actions are carried out in areas of large deposits. In small deposits, limestone is mainly mined using the explosive method. From such deposits, stone is extracted in the form of rectangular blocks. This occurs due to the creation of contour gaps.
It is worth noting that each of the methods is economically expensive to one degree or another. However, one of the cheapest options is to extract stone using an excavator and a hydraulic breaker. But there is the most economical way, which is to use a mining machine. This method is approximately 7% cheaper than the previous one.
Limestone is a sedimentary rock of organic origin. There is also a chemogenic origin of limestone, when the rock is formed as a result of chemical precipitation during the evaporation of water or from aqueous solutions. The basis of the rock is considered to be predominantly calcium carbonate, presented in the form of calcite crystals of different sizes. Limestone mining is in demand because people use this rock in many areas.
Description
The basis of limestone is calcium carbonate, a substance that can dissolve in water. As a result, karst is formed. It can decompose into bases and carbon dioxide. This is carried out at great depths, because due to the influence of the Earth’s heat, limestone forms gas for mineral waters.
Limestone may include admixtures of clay minerals, dolomite, quartz, gypsum, and pyrite. Natural limestone is light gray in color, although it can be black or white. Impurities give a blue, pink, yellow tint. Limestone mining is in demand due to its widespread use. The breed is durable and known for its unique characteristics that make it unlike other materials.
Classification
A common type of rock is shell rock, which consists of shells of marine animals and their fragments. There are other types of limestone:
- Bryozoan, which includes the remains of bryozoans - small invertebrate animals that live in colonies in the seas.
- Nummulite, consisting of extinct single-celled nummulite organisms.
- Marbled. It can be thin-layered or massively layered.
During metamorphism, a process of recrystallization occurs with limestone, due to which this rock forms marble. 
Limestone is considered a monomineral rock, the method of extraction of which may differ depending on the type of impurities, structure, and geological age. There are organizations that are engaged in extracting limestone. Places and methods of extraction are determined by terrain, types of rocks and other characteristics.
Place of Birth
As can be seen from the above, limestone is considered a sedimentary rock that appeared with the participation of living organisms living in sea basins. The breed is mined in many regions of our country and other countries. Russia is considered one of the leaders in its availability.
Limestone is considered the "building material" of mountain ranges. An example is the Alps, although it can occur in other mountainous regions. Mining of limestone stone occurs all over the world. There are many reserves in our country. Moreover, all limestone mining sites make it possible to obtain different breeds natural materials: dense, white, flux, shell-oolitic.
Limestone mining is known in Russia. Popular deposits are in the western part of the country. Developments are carried out from the Belgorod and Tula regions to Moscow, Vologda, Voronezh regions. Mining takes place near St. Petersburg, in Krasnodar region, Arkhangelsk, in the Urals, in Siberia. Among neighboring countries, there are deposits in the Donetsk region of Ukraine.
Extraction methods
Mining is carried out using an open pit method. The top layer of soil and clay is removed. This is how a quarry is formed. Limestone mining involves performing pyrotechnic work to crush and separate portions of rock. Then it is transported by car for processing. 
The world's first extraction method is considered to be the breaking method. This name was obtained due to the fact that the rock was removed with crowbars, and then the stones were knocked out of the formation with hammers. An alternative to this method is now being used. The blasting method is used. The rock produces fine crumbs. An excavator collects it, loads it onto dump trucks, and then everything is transported to the plant, where processing and cleaning are carried out.
There is a special device for an excavator with which limestone extraction can be carried out without an explosion. The driver exchanges the bucket for an attachment that loosens the rock. This method is used in areas with high population density. There is a mining method using a milling combine. This is the most profitable option. At the same time, mining, crushing, and transportation of rock are carried out.
Features of the traditional method
The old method is used to extract limestone slabs. You just need to find a way out from underground. Then a shovel is used to clear the area where mining will take place. 
Use a crowbar to create a crack in the limestone slab, and then pry the edge of the slab and lift it. Since the limestone is located underground in layers, only a small plate of it should be lifted. It must be pulled out from the place where the limestone lies. They cut the rock with a regular saw. To simplify the work, the tool is moistened in water.
Explosive method
Limestone is produced using the explosive method. First, you need to open up the deposits, removing earth, clay and substandard limestone from them using bulldozers. Wells are drilled near the edge of the mining site and explosives are placed there. With the help of explosions, layers of limestone are broken off, which then needs to be loaded into dump trucks and taken out for further processing. 
Then the quarry where the mining took place is filled with earth and planted with herbs and plants. This method is used in large fields. And in small ones you should not use the explosive method. Then the limestone is removed in blocks similar to the shape of rectangles. This technology is called bar mining.
The work is carried out by different machines that cut stones. An excavator is a must. The technology has its advantages:
- Simplicity.
- Good block shape.
- Easy transportation and handling.
Since limestone has a porous structure, it is used in construction business. Temples, palaces, and estates are built from it.
Types and colors of limestone
Limestone mining produces a variety of rocks. They differ in color, structure, chemical composition, origin, area of use and other characteristics. Depending on the type of application, limestones are found in different colors:
- White and gray are “pure” breeds that contain no impurities.
- Red and brown - limestones with manganese.
- Yellow and brown - contain iron.
- Green - stones with inclusions of seaweed.
- Dark gray and black - have organic impurities.
According to its structure and chemical composition, the rock can be:
- Dolomitized - contains 4-17% magnesium oxide. If the proportion of magnesium increases, dolomites are formed.
- Marbled - carbonate limestones with organic inclusions. Their palette can range from beige to gray-blue tones.
- Coral. The rocks have a porous structure. They are transformed into reefs from mollusk shells and the shells of marine life.
- Clayey. The rock has a composition similar to limestone and marl. The formations are softer than limestones, brittle compared to shale clays.
By origin, limestones are:
- Jurassic is a rock with a history of hundreds of millions of years, has high strength, density and fine grain size. In the Middle Ages, limestone was called "marble" because it could be polished.
- Putilovsky. This limestone has unique physical characteristics, low moisture absorption and abrasion. During the formation of St. Petersburg it was the main building material. It is named after the place of production - the Putilovsky quarry, located in the Leningrad region.
Application options
In the metallurgical industry it is used as a flux. It is considered the main component during the creation of cement and lime. It is used as an auxiliary component for the production of soda, mineral fertilizers, paper, sugar, and glass. 
The material is also used to produce rubber, paints, soap, plastics, and mineral wool. It is in demand in the construction field for the production of facing and wall blocks. It is used for the construction of foundations and roads. Limestone mining makes it possible to supply the entire country with building materials.
Limestone is a fairly valuable natural resource. The scope of use of limestone materials is quite wide. Of course, it is worth considering that, like all natural resources, it can be exhausted.
There are quite a lot of limestone deposits all over the world; this rock is not rare, but depending on the mining methods and the technology used, it can be quite different in its structure.
As for Russia, the number of quarries for the extraction of limestone rock is quite large; they are found in almost every corner. The following regions are quite well known and given publicity: Voronezh, Leningrad, Tula, Arkhangelsk, Belgorod, Vologda.
Of course, we should not forget about the deposits located in the Krasnodar Territory, in the Urals, in the Moscow region, as well as in some areas of Siberia.
In the Vologda region, a deposit of limestone rocks is under development, and the resources that are mined there are used for a lime plant located nearby.
The Slobodskoye deposit is less known, as it is located on the territory of a closed railway station.
The Novo-Pristanskoye field is located on the territory of the municipal Satkinsky district. IN this moment Limestone reserves amount to more than 8 thousand tons.
The most popular among enterprises that use limestone as the main raw material in their production are the Savinskoye and Shvakinskoye deposits. It is located in the Arkhangelsk region and includes the Shestovsky, Ogarkovsky and Left Bank areas.
The resources that are mined here are used in cement production. According to the balance sheet, limestone reserves amount to about 106,000 thousand tons. Of this volume, about 65,020 thousand tons are in the undistributed fund. The rest of the volume is in the process of preparation, development and technical training limestone mining project.
The Shvakinskoye field is located in the Arkhangelsk region, namely in the urban settlement of Obozer. This section consists of two territories - Left Bank and Eastern. The left bank section is considered a reserve fund, i.e. no activities are being carried out here regarding the development of methods for extracting limestone.
The eastern part is used quite intensively, and today the annual production volume is 100 thousand tons per year. The limestone extracted from this quarry is used for the cement industry.
Thus, we can say that Russia is a fairly rich country in terms of resource reserves. 
Sedimentary rock of organic, less often chemogenic origin, consisting primarily of calcium carbonate in the form of calcite crystals of various sizes.
Limestone, consisting mainly of shells of marine animals and their fragments, is called shellweed. In addition, there are nummulitic, bryozoan and marble-like limestones - massively layered and thin-layered. During metamorphism, limestone recrystallizes and forms marble.
Calcium carbonate, which is part of limestone, can slowly dissolve in water and also decompose into carbon dioxide and corresponding bases. The first process is the most important factor in the formation of karst, the second, occurring at great depths under the influence of the deep heat of the Earth, provides a source of gas for mineral waters.
Application area
Limestone brick Limestone is most widely used as construction material. The strength of many types of limestone is sufficient for the construction of multi-story buildings. Thin layers of wear-resistant stone - limestone - are a ready-made material, such limestone is used to clad buildings and pave paths.
Layered limestone with a pronounced weathering relief is valued by decorators, designers and landscape architects.
Manufacturers of natural stone products often successfully play up the biological origin of the rock. The shells of ancient mollusks, preserved in limestone deposits, become an important expressive element finishing materials. Cement is also indispensable for any construction - which, in turn, is made from a percentage-controlled mixture of limestone and clay.
Limestone marl Marl is the name of the variety, which contains the required amount of aluminosilicates. It is mined in many regions of the world.
How is limestone mined?
Limestone can be mined using the explosive method. To do this, you first need to open up the deposits by removing the soil from them using bulldozers. It is also necessary to remove clay and substandard limestone from them. It is necessary to drill holes along the edge of the mining site and place explosives there. If the explosions are organized correctly, they will break off large layers of limestone, which then need to be loaded into dump trucks and taken to the processing site.
The area from which overburden is removed depends on the annual demand for lime and the thickness of the limestone layer.
So, for example, if the annual demand for lime is 500 tons, then it is necessary to burn approximately 1000 tons of limestone.
When crushing limestone, waste is obtained in the form of small crushed stone, and losses occur partially during its transportation, which is about 25%. Consequently, to extract 1250 tons of limestone (with a mass of 1 m3 of about 2 tons), it is necessary to mine 625 m3 of it.
To obtain an annual supply of limestone with an average thickness of the layer, taking into account its possible interlayers in the overburden, equal to 2 m, it is necessary to free the area from overburden: 625: 2 = 312.5 m2.
If possible, overburden is removed with bulldozers and excavators during the warm season.
The selected infertile soil is transported from the development site as the overburden is removed into ravines, depressions, and excavations.
LIMESTONE MINING
Methods for developing limestone depend on the structure and nature of the strata. Limestone layers can be arranged in layers horizontally or with a certain angle of inclination to the horizon. There are limestones with almost vertically arranged layers.
In limestones with a layered structure, there are usually layers of clay between the layers; in addition, the layers are often cut through by cracks, which makes it easier to break out the limestone.
To mine such limestone, a crowbar is driven into the interlayer between the layers, a hard object is placed under it (another crowbar, a hammer or a strong stone), and by pressing on the free piece of the crowbar, the slab is lifted. Typically, pieces of limestone are easily separated along the layers and cracks.
If the limestone is a solid mass and has few cracks, then to facilitate breaking out the blocks from above the massif, a pick is cut out with a pick in the place where it is desirable to separate the block from the formation. Then the layer is tamped down with a crowbar and the block is broken out using the usual method. The height of the separated block should not exceed 0.8... 1 m.
With a horizontal arrangement of layers, as well as with a small angle of inclination, the development of layers is carried out in any direction. It is somewhat easier to develop development towards the direction of fall of the layers. But this is only allowed if the slope of the layers is small and does not exceed the angle of inclination at which the broken blocks can themselves roll down the exposed layers. If the limestone layers are located at a steep angle, it is developed in the opposite direction.
When developing limestone deposits, it is necessary to comply with safety and labor protection requirements. The work can be carried out using ledges, breaking out stone simultaneously on two or even more layers of limestone. The height of the ledge should not exceed 2 meters, the base should have a flat area cleared of debris with a width of at least 0.7 m. Sheer walls should be given a slight slope, 10...15 cm for each meter of height.
In no case should the second ledge come close to the slope of the first, so that there is no shedding of limestone from the surface of the wall of previously mined layers (located above the ledge).
Limestone blocks broken out of a massif or from a layer are broken into smaller pieces with sledgehammers and stored in stacks no more than 2 m high. In plan, the stacks must have a regular rectangular shape, which makes it easier to measure them and calculate the volume of the stone.
A limestone warehouse is arranged near the place of firing. For this purpose, it is necessary to select a flat, excavated area that is not flooded with water.
LIMESTONE KILNING IN A KILN
Lime kilns are of various types. The most accessible for collective farms are shaft furnaces of low power (11).
The walls of the furnace are laid out of brick. The furnace has a firebox, which serves for the initial kindling of the furnace. The discharge opening is located above the grate. Limestone is fired using the pouring method with layer-by-layer loading of stone and anthracite coal into the shaft. For ease of loading, the furnace is located on the slope of a ravine or on a steep slope. It is more advisable to locate the furnace directly in the quarry, on the slope of the excavation.
First, firewood is loaded onto the grate, on which the first layer of stone of the same size is laid with a layer thickness of 25...30 cm. Then anthracite coal is poured over the leveled surface of the stone lining in a layer of no more than 8 cm (according to calculations).
In batch kilns, coal consumption per 1 ton of lime is 300...400 kg. Subsequent loading of stone and fuel is carried out with the same alternation of layers.
To reduce the temperature effect on the walls during fuel combustion, the thickness of the coal layer near the walls is reduced.
The stove is first loaded with stone and fuel at approximately 2/3 of the stove's height, then firewood is placed under the grate and ignited. After heating the furnace, continue loading the furnace to the top. After this, the walls are built up by laying dry stone to a height of up to 70 cm and the increased volume of the furnace is filled with fuel. After the firing is completed, the volume of stone charging in the kiln will decrease and the lime will drop to the level of the top of the main volume of the kiln.
The finished lime is unloaded through the unloading hole, for which the brick is removed from it.
To obtain 1 ton of lime, it is required to burn 1.2 ... 1.4 m3 of limestone. Lime must comply with GOST 9179-77.
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