Basic chemical elements of the earth's crust. Structure and composition of the earth's crust

For those people who did not listen attentively to the teacher at school, it will be interesting to know that the main element that makes up the earth's crust is oxygen.

The earth's crust, its features

What to do about this natural disaster?

It is impossible to prevent an earthquake. The forces that provoke this disaster are beyond the control of man, for their source lies much deeper than humanity has been able to penetrate. We are only “picking” the top layer (so far within 13 kilometers), at a time when the deepest recorded location of the earthquake epicenter was 750 kilometers.

But everything was done to foresee a possible disaster, its strength and location. Seismographs are used for this.

Constant research makes it possible to create a picture of seismological activity and take this into account during construction. Engineers, in turn, are working on new designs that can withstand such activity. Constant work is underway to inform the population about how to behave in the event of an earthquake.

A terrible phenomenon that can arise as a result of such a disaster is a tsunami. Thus, in 2011, huge waves of ocean water devastated the lands of Northeastern Japan, as a result of which about 16 thousand people died, and more than a million buildings were completely or partially destroyed. Including three reactors at the Fukushima-1 nuclear power plant. Over three hundred thousand people were left homeless. The same event affected the speed of rotation of the Earth, but this is hardly noticeable to humans, since the day became shorter by only 1.8 microseconds. So, having touched on the topic of what the main element that makes up the earth’s crust is, we moved on to problems that may arise due to the processes hidden by it.

MAIN CHARACTERISTICS OF THE LITHOSPHERE

Lithosphere formation

After the mass of the planet reached approximately its modern value about 4.6 billion years ago, its self-heating began. There were two sources of heat - gravitational compression and radioactive decay. As a result, the temperature inside the Earth began to rise and the melting of metals began. The mantle was formed as a result of differentiation of primary matter by density. Iron and nickel, having sank, concentrated in the core, and a relatively light substance, pyrolite, accumulated in the mantle. The process of differentiation of mantle matter continues to this day.

Structure of the Earth

With modern technical means, we cannot directly observe and study the deep layers of the Earth. The deepest borehole on Earth does not reach 8 km. Deeper layers are studied by indirect geophysical methods, on the basis of which one can only build hypotheses. The most important is the seismic method, which, based on the speed of propagation of elastic waves in the Earth caused by an earthquake or artificial explosions, makes it possible to judge the elastic properties of matter located at different depths. Thus, based on numerous measurements, it has been established that the speed of propagation of seismic waves changes abruptly at certain depths. This is due, first of all, to the abrupt change in the density of the Earth's layers (Table 8.2.1).

The first section zone, called Mohorovicic zone, located at an average depth of 33 km , the second is at an average depth of 2900 km. These zones divide the Earth into three main layers: crust, mantle and core(Figure 8.2.1).

Bark- the upper solid rock shell of the Earth. Based on physical properties, the bark is divided into three layers: sedimentary, granite and basalt(Figure 8.2.2) . Based on thickness and structure, there are two main types of crust: continental and oceanic.

Figure 8.2.1 – Shells of the Earth, distinguished by the speed of passage of seismic waves

(Bogomolov, Sudakova, 1971)

in the intermediate zone between them there is a transitional type of crust. The continental crust has an average thickness of 35 km (up to 80 km in mountainous countries) and consists of three layers: sedimentary with a thickness of 0 - 15 km, granite with an average thickness of 10 km and basalt with an average thickness of 20 km. Sediments are mainly represented by clays, sands and limestones. The thickness of the oceanic crust is on average 5 km: the sedimentary layer is about 1.5 km thick, the granite layer is absent, and the basaltic layer is about 5 km thick. The names granite and basalt were given to them not for their mineralogical composition, but because the speed of passage of seismic waves in these layers corresponds to the speed of seismic waves in granite and basalt.

Figure 8.2.2 – Structure of the earth’s crust: 1 – water, 2 – sedimentary layer, 3 – granite layer,

4 – basalt layer, 5 – mantle (Neklyukova, 1975)

Continuous changes are taking place in the life of the earth's crust - large depressions and uplifts are forming and developing. In stable areas, the so-called platform, uplifts and troughs are measured in hundreds of kilometers, and the speed of vertical movements is measured in fractions of a millimeter per year. In mobile, so-called geosynclinal zones, troughs and uplifts have an elongated shape of the order of 50–100 km, and the speed of vertical movement is about 1 cm per year. The reason for the vertical movements lies in the Earth's mantle.

Mantle– the shell of the Earth, differing from the crust mainly in physical parameters. It consists of oxides of magnesium, iron and silicon, which form magma. The pressure in the mantle increases with depth and reaches 1.3 million atmospheres at the core boundary. The density of the mantle increases from 3.5 in the upper layers to 5.5 g/cm 3 at the core boundary. The temperature of the mantle material accordingly increases from approximately 500°C to 3800°C. Despite the high temperature, the mantle is in a solid state.

At depths of 100 to 350 km, especially between 100 and 150 km, the combination of temperature and pressure is such that the substance is in a softened or molten state. This layer of melting and increased activity is called asthenosphere, Sometimes - waveguide. Convection currents generate horizontal asthenospheric currents. Their speed reaches several tens of centimeters per year. These currents led to the splitting of the lithosphere into separate blocks and to their horizontal movement, known as continental drift. The asthenosphere contains volcanic foci and centers of deep-focus earthquakes.

The lower boundary of the lithosphere is drawn above the asthenosphere. The life of the earth's crust, its vertical and horizontal movements, volcanism and earthquakes are closely related to the upper mantle. Therefore, in the lithosphere, modern science includes the earth’s crust and the uppermost mantle to the asthenosphere, to a depth of about 100 km.

The mantle extends from the earth's crust to a depth of 2900 km, where it borders the core located in the middle of the Earth.

Table 8.2.1 – Depths and basic properties of geospheres (Shubaev, 1979)

Core- the central part of the Earth of not entirely clear chemical and physical nature. Since the beginning of the 20th century. there is a hypothesis that the core is 85–90% iron; in the outer liquid core oxygen is added to it, and in the inner liquid core nickel is added. According to modern data, the silicate core hypothesis has more supporters. However, regardless of the composition of the chemical elements, the nucleus, due to special physical conditions, is characterized by complete degeneration of the chemical properties of the substance. The temperature of the core is about 4000°C, the pressure in the center of the Earth is more than 3.5 million atmospheres. Under such conditions, the substance passes into the so-called metallic phase, the electron shells of atoms are destroyed and electron plasma of individual chemical elements is formed. The substance becomes more dense and saturated with free electrons. Huge ring vortices of free electrons arising in the core probably generate a constant magnetic field of the Earth, which extends into near-Earth space over several Earth radii. The formation of the magnetosphere and the isolation of the earth's nature from the plasma of the solar corona was the first and one of the most important conditions for the origin of life, the development of the biosphere and the formation of the geographical envelope.

The outer core is liquid. The density of the outer core in the upper part is about 10.0 g/cm3 . The inner core is solid, its density reaches 13.7 g/cm3.

Chemical composition of the earth's crust

The distribution of chemical elements in the earth's crust was first quantified by the American scientist F.W. Clark. In his honor, the average value of the relative content of a chemical element in the earth’s crust is usually called Clark.

All elements of the earth’s crust, according to their clarke, can be divided into two groups:

1. Elements with large clarks. This group includes (clarks are given according to Vinogradov, 1960):

The sum of these 8 elements is 99.03%. The same group includes hydrogen (H - 0.1%) and titanium (Ti - 0.7%). The elements of this group form independent chemical compounds, they are called main.

1. Elements with low clarke. This group includes all the other elements in the earth’s crust; they are mostly dispersed among the chemical compounds of other elements, they are called scattered

The average content of a chemical element equal to 0.1% is conventionally taken as the boundary between groups. The earth's crust is dominated by light atoms, occupying the initial cells of the periodic table, the nuclei of which contain a small number of protons and neutrons. Elements with even atomic numbers and atomic masses also predominate.

Processes occurring in the depths of the Earth influence the formation of rocks, earthquakes and volcanic eruptions, slow vibrations of the land surface and seabed, and other phenomena that transform the Earth's surface. Therefore, when studying the geographical shell, it is necessary to know the structure of the Earth and the nature of its internal layers.

The upper rocky shell of the Earth - the earth's crust - is composed of rocks of different composition and origin. Any rock is a certain combination of minerals, which, in turn, are chemical elements or their natural compounds.

Thus, the substance of the earth's crust, in order of complexity of the degree of its organization, forms a hierarchical series: chemical element - mineral - rock. It is in this sequence that the material composition of the earth’s crust is considered below.

The most reliable information about the chemical composition of the earth's crust relates to its upper part (to a depth of 16-20 km), accessible for direct study. The still relatively young science of geochemistry deals with the problems of chemical composition and the patterns of its changes in space and time.

According to modern geochemistry, 93 chemical elements are found in the earth's crust. Most of them are complex, that is, they are represented by a mixture of different isotopes. Only 22 chemical elements (for example, sodium, manganese, fluorine, phosphorus, gold) do not have isotopes and are therefore called simple.

Chemical elements are distributed extremely unevenly in the earth's crust.

The first serious studies concerning the prevalence of chemical elements were carried out by the American geochemist F. Clark. By mathematically processing the results of 6,000 chemical analyzes of various rocks at his disposal, F. Clark established the average contents of the 50 most common chemical elements in the earth's crust. F. Clark's data, published for the first time in 1889, was subsequently refined by many domestic and foreign researchers: G. Washington, V. Golschmidt, G. Hevesi, V. Mason, V. I. Vernadsky, A. E. Fersman, A. P. Vinogradov, A. A. Yaroshevsky and others.

As a sign of F. Clark's special merit to geochemical science, the average contents of chemical elements in the earth's crust are called Clarks and are expressed in weight, atomic or volume percentages. The most and frequently used weight clarks of elements. The table below shows the clarks of the most common elements of the earth's crust according to various researchers.

Weight clarke of the most common chemical elements in the earth's crust.

The data presented show that the main building elements of the earth's crust are O, Si, Al, Fe, Ca, Na, K, Mg, constituting more than 98% of its weight. The leading place among them belongs to oxygen, which accounts for almost half the mass of the earth’s crust and about 92% of its volume. Based on the predominant chemical elements, the earth's crust is sometimes called the oxysphere, as well as the sialic shell.

The prevalence of chemical elements is related to their position in the periodic table. As D.I. Mendeleev noted, the most common elements of the earth’s crust are located at the beginning of the periodic table. As the serial number increases, the prevalence of elements decreases unevenly.

Thus, among the first 30 elements, clarks rarely fall below hundredths of a percent and are more often expressed in tenths or even whole percentages. The remaining elements are dominated by small clarkes, which only very rarely rise to thousandths of a percent.

Thus, light elements clearly predominate in the earth’s crust, which distinguishes it from other internal geospheres, which are poorer in these elements and enriched in heavy metals. The relationship between the clarks of chemical elements and their position in the periodic table suggests that one of the main reasons for the different abundance of chemical elements in the earth's crust is the structure and energy stability of the nuclei of their atoms.

It should be noted that our ideas about the abundance of chemical elements do not always agree with the true values ​​of their clarke values. For example, such common elements as copper, zinc, and lead have clarke values ​​that are many times smaller than zirconium and vanadium, which are considered rare. The reason for this discrepancy is the different ability of chemical elements to form significant concentrations in the earth's crust - deposits. This ability is determined by their chemical properties, which depend on the structure of the outer electron shells of atoms, as well as the thermodynamic conditions of the earth's crust.

The chemical composition of the earth's crust changes over geological time, and this evolution continues to this day. The main reasons for changes in the chemical composition are:

Radioactive decay processes leading to spontaneous

the transformation of some chemical elements into others, more stable in the conditions of the earth's crust. According to the calculations of V.I. Vernadsky, in the modern era, only due to nuclear transformations do the substances of the earth’s crust annually update their chemical composition;

Intake of meteoric matter in the form of meteorites and cosmic dust (16 thousand tons annually);

Continuing processes of differentiation of the Earth's substance, leading to the migration of chemical elements from one geosphere to another.

Atoms of chemical elements in the earth's crust form various combinations with each other, mainly chemical compounds. The forms of their occurrence are quite diverse, but the main form of existence of chemical elements in the earth’s crust is mineral. Moreover, in some cases they form independent mineral species, in others they enter the crystal lattices of other minerals in the form of impurities.

A characteristic feature of the evolution of the Earth is the differentiation of matter, the expression of which is the shell structure of our planet. The lithosphere, hydrosphere, atmosphere, biosphere form the main shells of the Earth, differing in chemical composition, thickness and state of matter.

Internal structure of the Earth

Chemical composition of the Earth(Fig. 1) is similar to the composition of other terrestrial planets, such as Venus or Mars.

In general, elements such as iron, oxygen, silicon, magnesium, and nickel predominate. The content of light elements is low. The average density of the Earth's substance is 5.5 g/cm 3 .

There is very little reliable data on the internal structure of the Earth. Let's look at Fig. 2. It depicts the internal structure of the Earth. The Earth consists of the crust, mantle and core.

Rice. 1. Chemical composition of the Earth

Rice. 2. Internal structure of the Earth

Core

Core(Fig. 3) is located in the center of the Earth, its radius is about 3.5 thousand km. The temperature of the core reaches 10,000 K, i.e. it is higher than the temperature of the outer layers of the Sun, and its density is 13 g/cm 3 (compare: water - 1 g/cm 3). The core is believed to be composed of iron and nickel alloys.

The outer core of the Earth has a greater thickness than the inner core (radius 2200 km) and is in a liquid (molten) state. The inner core is subject to enormous pressure. The substances that compose it are in a solid state.

Mantle

Mantle- the Earth’s geosphere, which surrounds the core and makes up 83% of the volume of our planet (see Fig. 3). Its lower boundary is located at a depth of 2900 km. The mantle is divided into a less dense and plastic upper part (800-900 km), from which it is formed magma(translated from Greek means “thick ointment”; this is the molten substance of the earth’s interior - a mixture of chemical compounds and elements, including gases, in a special semi-liquid state); and the crystalline lower one, about 2000 km thick.

Rice. 3. Structure of the Earth: core, mantle and crust

Earth's crust

Earth's crust - the outer shell of the lithosphere (see Fig. 3). Its density is approximately two times less than the average density of the Earth - 3 g/cm 3 .

Separates the earth's crust from the mantle Mohorovicic border(often called the Moho boundary), characterized by a sharp increase in seismic wave velocities. It was installed in 1909 by a Croatian scientist Andrei Mohorovicic (1857- 1936).

Since the processes occurring in the uppermost part of the mantle affect the movements of matter in the earth's crust, they are combined under the general name lithosphere(stone shell). The thickness of the lithosphere ranges from 50 to 200 km.

Below the lithosphere is located asthenosphere- less hard and less viscous, but more plastic shell with a temperature of 1200 ° C. It can cross the Moho boundary, penetrating into the earth's crust. The asthenosphere is the source of volcanism. It contains pockets of molten magma, which penetrates into the earth's crust or pours out onto the earth's surface.

Composition and structure of the earth's crust

Compared to the mantle and core, the earth's crust is a very thin, hard and brittle layer. It is composed of a lighter substance, which currently contains about 90 natural chemical elements. These elements are not equally represented in the earth's crust. Seven elements - oxygen, aluminum, iron, calcium, sodium, potassium and magnesium - account for 98% of the mass of the earth's crust (see Fig. 5).

Peculiar combinations of chemical elements form various rocks and minerals. The oldest of them are at least 4.5 billion years old.

Rice. 4. Structure of the earth's crust

Rice. 5. Composition of the earth's crust

Mineral is a relatively homogeneous natural body in its composition and properties, formed both in the depths and on the surface of the lithosphere. Examples of minerals are diamond, quartz, gypsum, talc, etc. (You will find characteristics of the physical properties of various minerals in Appendix 2.) The composition of the Earth's minerals is shown in Fig. 6.

Rice. 6. General mineral composition of the Earth

Rocks consist of minerals. They can be composed of one or several minerals.

Sedimentary rocks - clay, limestone, chalk, sandstone, etc. - were formed by the precipitation of substances in the aquatic environment and on land. They lie in layers. Geologists call them pages of the history of the Earth, since they can learn about the natural conditions that existed on our planet in ancient times.

Among sedimentary rocks, organogenic and inorganogenic (clastic and chemogenic) are distinguished.

Organogenic Rocks are formed as a result of the accumulation of animal and plant remains.

Clastic rocks are formed as a result of weathering, destruction by water, ice or wind of the products of destruction of previously formed rocks (Table 1).

Table 1. Clastic rocks depending on the size of the fragments

Chemogenic Rocks are formed as a result of the precipitation of substances dissolved in them from the waters of seas and lakes.

In the thickness of the earth's crust, magma forms igneous rocks(Fig. 7), for example granite and basalt.

Sedimentary and igneous rocks, when immersed to great depths under the influence of pressure and high temperatures, undergo significant changes, turning into metamorphic rocks. For example, limestone turns into marble, quartz sandstone into quartzite.

The structure of the earth's crust is divided into three layers: sedimentary, granite, and basalt.

Sedimentary layer(see Fig. 8) is formed mainly by sedimentary rocks. Clays and shales predominate here, and sandy, carbonate and volcanic rocks are widely represented. In the sedimentary layer there are deposits of such minerals, like coal, gas, oil. All of them are of organic origin. For example, coal is a product of the transformation of plants of ancient times. The thickness of the sedimentary layer varies widely - from complete absence in some land areas to 20-25 km in deep depressions.

Rice. 7. Classification of rocks by origin

"Granite" layer consists of metamorphic and igneous rocks, similar in their properties to granite. The most common here are gneisses, granites, crystalline schists, etc. The granite layer is not found everywhere, but on continents where it is well expressed, its maximum thickness can reach several tens of kilometers.

"Basalt" layer formed by rocks close to basalts. These are metamorphosed igneous rocks, denser than the rocks of the “granite” layer.

The thickness and vertical structure of the earth's crust are different. There are several types of the earth's crust (Fig. 8). According to the simplest classification, a distinction is made between oceanic and continental crust.

Continental and oceanic crust vary in thickness. Thus, the maximum thickness of the earth’s crust is observed under mountain systems. It is about 70 km. Under the plains the thickness of the earth's crust is 30-40 km, and under the oceans it is thinnest - only 5-10 km.

Rice. 8. Types of the earth's crust: 1 - water; 2- sedimentary layer; 3—interlayering of sedimentary rocks and basalts; 4 - basalts and crystalline ultrabasic rocks; 5 – granite-metamorphic layer; 6 – granulite-mafic layer; 7 - normal mantle; 8 - decompressed mantle

The difference between the continental and oceanic crust in the composition of rocks is manifested in the fact that there is no granite layer in the oceanic crust. And the basalt layer of the oceanic crust is very unique. In terms of rock composition, it differs from a similar layer of continental crust.

The boundary between land and ocean (zero mark) does not record the transition of the continental crust to the oceanic one. The replacement of continental crust by oceanic crust occurs in the ocean at a depth of approximately 2450 m.

Rice. 9. Structure of the continental and oceanic crust

There are also transitional types of the earth's crust - suboceanic and subcontinental.

Suboceanic crust located along continental slopes and foothills, can be found in marginal and Mediterranean seas. It represents continental crust with a thickness of up to 15-20 km.

Subcontinental crust located, for example, on volcanic island arcs.

Based on materials seismic sounding - the speed of passage of seismic waves - we obtain data on the deep structure of the earth’s crust. Thus, the Kola superdeep well, which for the first time made it possible to see rock samples from a depth of more than 12 km, brought a lot of unexpected things. It was assumed that at a depth of 7 km a “basalt” layer should begin. In reality, it was not discovered, and gneisses predominated among the rocks.

Change in temperature of the earth's crust with depth. The surface layer of the earth's crust has a temperature determined by solar heat. This heliometric layer(from the Greek helio - Sun), experiencing seasonal temperature fluctuations. Its average thickness is about 30 m.

Below is an even thinner layer, the characteristic feature of which is a constant temperature corresponding to the average annual temperature of the observation site. The depth of this layer increases in continental climates.

Even deeper in the earth's crust there is a geothermal layer, the temperature of which is determined by the internal heat of the Earth and increases with depth.

The increase in temperature occurs mainly due to the decay of radioactive elements that make up rocks, primarily radium and uranium.

The amount of temperature increase in rocks with depth is called geothermal gradient. It varies within a fairly wide range - from 0.1 to 0.01 °C/m - and depends on the composition of rocks, the conditions of their occurrence and a number of other factors. Under the oceans, temperature increases faster with depth than on continents. On average, with every 100 m of depth it becomes warmer by 3 °C.

The reciprocal of the geothermal gradient is called geothermal stage. It is measured in m/°C.

The heat of the earth's crust is an important energy source.

The part of the earth's crust that extends to depths accessible to geological study forms bowels of the Earth. The Earth's interior requires special protection and reasonable use.

Analysis of the chemical and mineral composition of the Earth has significant theoretical and practical interest: it can reveal many secrets of the formation and evolution of our planet and provide the key to a more effective search for mineral resources. The average composition of the Earth is judged by the substance from which meteorites are composed, since it is believed that it was from this material that the planets of the solar system, including the Earth, once originated. There are stone (97.7% of all finds), stony-iron (1.3%) and iron (5.6%) meteorites. Their chemical analysis suggests that the composition of the Earth is dominated by iron (30-36%), oxygen (29-31%), silicon (14-15%) and magnesium (13-16%). In addition, the amount of sulfur, nickel, aluminum and calcium is measured in units of percent each. All other elements are present in amounts less than 1%.

The most reliable information is available about the chemical composition of the uppermost part of the continental crust, accessible for direct observation and analysis. The first data were published in 1889 by the American scientist F. Clark, who obtained them as arithmetic averages of 6,000 results of chemical analysis of various rocks at his disposal. These data were subsequently refined. The following eight chemical elements are most common in the earth's crust, accounting for a total of over 98% by weight: oxygen (46.5%), silicon (25.7%), iron (6.2%), calcium (5.8%). ), magnesium (3.2%), sodium (1.8%), potassium (1.3%). Five more elements are contained in the earth's crust in tenths of a percent: titanium (0.52%), carbon (0.46%), hydrogen (0.16%), manganese (0.12%), sulfur (0.11%). %). All other elements account for about 0.37%.

In 1924, Norwegian researcher V.M. Goldschmit proposed the widely used and currently geochemical classification of chemical elements, dividing them into four groups:

• 0 siderophile group of chemical elements includes elements of the iron family, platinum metals, as well as molybdenum and rhenium (11 elements in total), which are similar in geochemical characteristics to iron;
• 0 lithophile elements constitute a group of 53 elements that make up the bulk of the minerals of the earth’s crust (lithosphere): silicon, titanium, zirconium, fluorine, chlorine, aluminum, sodium, potassium, magnesium, calcium, etc.;
• 0 chalcophile group of chemical elements is represented by sulfur, antimony, bismuth, arsenic, selenium, tellurium and a number of heavy non-ferrous metals (copper, etc.) - a total of 19 elements prone to the formation of natural sulfides, selenides, tellurides, sulfosalts and sometimes found in native state (gold, silver, mercury, bismuth, arsenic, etc.);

The atmophilic group includes chemical elements (nitrogen, hydrogen, noble gases) typical of the earth’s atmosphere, in which they are present in the form of free atoms or molecules.

The earth's crust is made up of different groups of rocks, differing in their formation conditions and composition. Rocks are mineral aggregates, i.e. a certain combination of minerals. Minervas are natural chemical compounds or native chemical elements that arose as a result of certain physical and chemical processes occurring in the earth’s crust and on its surface. Most minerals are crystalline solids, and only a few are amorphous. The shapes of natural crystals are varied and depend on the regular arrangement in space of microparticles - atoms, ions, molecules that form the structure of the crystals, or their crystalline (spatial) lattice. For the formation of this structure, physicochemical and thermodynamic conditions are of great importance. Thus, graphite - the softest (hardness 1) mineral - forms tabular crystals, and diamond - the hardest mineral (hardness 10) - has the most perfect cubic symmetry group. This difference in properties is due to the difference in the arrangement of atoms in the crystal lattice.

Currently, more than 2,500 natural minerals are known, not counting varieties, but only a few (about 50) - rock-forming minerals - are involved in the formation of rocks that make up the earth's crust. The remaining minerals in rocks occur in the form of minor impurities and are called accessory minerals. The classification of minerals is based on their chemical composition and crystal structure. The main rock-forming and ore minerals are grouped into several mineral classes:

• 0 native elements: native gold, silver, copper, platinum, graphite, diamond, sulfur;
• 0 sulfides: pyrite, chalcopyrite, galena, cinnabar;

O halide compounds: halite (table salt), sylvite, carnallite and fluorite;

О oxides and hydroxides: quartz, opal, magnetite (magnetic iron ore), hematite, corundum, limonite, goethite;

O carbonates: calcite (lime spar), the transparent variety of which is called Iceland spar, dolomite;

O phosphates: apatite, phosphorite;

О sulfates: gypsum, anhydrite, mirabilite (Glauber's salt), barite;

About tungstates: wolframite;

O silicates: quartz, olivine, beryl, pyroxenes, hornblende, micas, serpentine, talc, glauconite, feldspars.

A special class of minerals are silicates. This class includes the most common rock-forming minerals in the earth’s crust (more than 90% by weight), extremely complex in chemical composition and participating in the structure of all types of rocks, primarily igneous and metamorphic. They make up about a third of all known minerals. Quartz is sometimes included in silicates. The basis of the crystal lattice of silicates is the ionic tetravalent group SiO 4.

Even ancient miners noticed that in ore deposits individual minerals are always found together. The joint occurrence of minerals is designated by the term “paragenesis” or “paragenesis” (Greek “para” - near, near). Each process of mineral formation is characterized by its own regular combinations of minerals. Examples of paragenesis include quartz and gold, chalcopyrite and silver ores. Knowledge of the paragenesis of minerals facilitates the task of searching for minerals by their satellites. Thus, the diamond's companion pyrope (a type of garnet) once helped to discover primary diamond deposits in Yakutia.

A certain combination of minerals, as mentioned above, forms rocks are natural aggregates of minerals of more or less constant mineralogical and chemical composition, forming independent geological bodies that make up the earth's crust. The shape, size and relative position of mineral grains determine the structure and texture of rocks. The rocks that make up the earth's crust are mostly an aggregate of many minerals; less often they consist of grains of one mineral. The mineral composition, structure and occurrence of a rock reflect the conditions of its formation.

Based on their origin, rocks are divided into three groups:

• 1) igneous rocks formed by intrusion (intrusive rocks) into the earth's crust or eruption of magma onto the surface (effusive rocks). Magma that flows to the surface is called lava. Many deposits of metallic minerals, as well as apatites, diamonds, etc., are associated with igneous rocks;
• 2) sedimentary rocks formed during the deposition of destroyed igneous rocks and some other ways in the ocean, seas, lakes and rivers. Their composition includes clastic, clayey, chemical and organogenic. The following sedimentary rocks are important as mineral resources: oil, gas, coal, peat, bauxite, phosphorite, etc.;
• 3) metamorphic breeds, i.e. transformed from both igneous and sedimentary. Under metamorphic conditions, iron, copper, polymetallic, uranium and other ores are formed, as well as graphite, precious stones, refractories, etc. Sometimes from the metamorphic group, metasomatic rocks are distinguished as an independent class, formed as a result of metasomatism - the process of replacing some minerals with others with significant changes in the chemical composition of the rock, but maintaining its volume and solid state when exposed to solutions of high chemical activity. In this case, migration of chemical elements occurs.