What is a mineral? Classification. The concept of minerals and their classification Minerals and their classification briefly

Plan.

Option number 6.

1. Classification of minerals and conditions of their formation: the main rock-forming minerals of exogenous and endogenous origin.

2. Glaciers, their geological role, distribution. Rocks formed as a result of the work of glaciers during the Ice Age.

3. Geotechnical research for industrial and civil construction.

4. Laboratory methods for determining the deformation and strength properties of soils.

5. Structure, texture, material composition of chemical and biochemical sedimentary rocks.

6. Inflow of pressure water into a perfect well.

Introduction.

Geology is a complex of sciences about composition and structure. The history of the development of the Earth, movements of the earth's crust and the placement of minerals in the bowels of the Earth. The main object of study, based on the practical tasks of man, is the earth's crust.

In recent decades, engineering geology has received special development - a science that studies the properties of rocks (soils), natural geological and technogenic-geological (engineering-geological) processes in the upper horizons of the earth's crust in connection with human construction activities.

The main goal of engineering geology is to study the natural geological situation of an area before the start of construction, as well as to predict the changes that will occur in the geological environment, and primarily in rocks, during the construction process and during the operation of structures. In modern conditions, not a single building or structure can be designed, constructed and reliably operated without reliable and complete engineering and geological materials.

1. Classification of minerals and conditions of their formation: the main rock-forming minerals of exogenous and endogenous origin.

Mineral– a natural body with a certain chemical composition and crystalline structure, formed as a result of natural physical and chemical processes and being an integral part of the earth’s crust, rocks, ores, and meteorites. The science of mineralogy is the study of minerals.

The earth's crust contains more than 7,000 minerals and their varieties. Most of them are rare and only a little more than 100 minerals are found frequently and in fairly large quantities and are part of certain rocks. Such minerals are called rock-forming minerals.

Origin of minerals. The conditions under which minerals are formed in nature are very diverse and complex. There are three main processes of mineral formation: endogenous, exogenous and metamorphic.

Endogenous process is connected with the internal forces of the Earth and manifests itself in its depths. Minerals are formed from magma - a silicate fiery liquid melt. In this way, for example, quartz and various silicates are formed. Endogenous minerals are usually dense, with great hardness, resistant to water, acids, and alkalis.

Exogenous process characteristic of the surface of the earth's crust. In this process, minerals are formed on land and in the sea. In the first case, their creation is associated with the weathering process, i.e. the destructive effects of water, oxygen, temperature fluctuations on endogenous minerals. In this way, clay minerals (hydromica, kaolinite, etc.), various ferruginous compounds (sulfides, oxides of chemical precipitation from aqueous solutions (halite, sylvite, etc.) are formed). In an exogenous process, a number of minerals are also formed due to the vital activity of various organisms (opal and etc.).

Exogenous minerals vary in properties. In most cases, they have low hardness and actively interact with water or dissolve in it.

Metamorphic process. Under the influence of high temperatures and pressures, as well as magmatic gases and water at some depth in the earth's crust, the transformation of minerals that were previously formed in exogenous processes occurs. Minerals change their original state, recrystallize, acquire density and strength. This is how many silicate minerals are formed (hornblende, actinolite, etc.).

Classification of minerals. There are many classifications of minerals. The most widely used classification is based on chemical composition and crystal structure. Substances of the same chemical type often have a similar structure, so minerals are first divided into classes based on chemical composition, and then into subclasses based on structural characteristics.

All minerals are divided into 10 classes.

Silicates- the most numerous class, including up to 800 minerals, which are the main part of most igneous and metamorphic rocks. Among silicates, there are groups of minerals characterized by some common composition and structure - feldspars, pyroxenes, amphiboles, micas, as well as olivine, talc, chlorites and clay minerals. All of them are aluminosilicates in composition.

Carbonates. These include more than 80 minerals. The most common are calcite, magnetism, and dolomite. The origin is mainly exogenous and associated with aqueous solutions. In contact with water, they slightly reduce their mechanical strength, although weakly, but they dissolve in water and are destroyed in acids.

Oxides and hydroxides. These two classes combine about 200 minerals, accounting for up to 17% of the total mass of the earth's crust. The most common are quartz, opal and limonite.

Sulfides contain up to 200 minerals. A typical representative is pyrite. Sulfides are destroyed in the weathering zone, so their admixture reduces the quality of building materials.

Sulfates. This class includes up to 260 minerals, the origin of which is associated with aqueous solutions. They are characterized by low hardness and light color. Relatively well soluble in water. The most common are gypsum and anhydrite. Upon contact with water, anhydrite turns into gypsum, increasing in volume up to 33%.

Halides contain about 100 minerals. The origin is mainly associated with aqueous solutions. The most widespread is halite. It can be a component of sedimentary rocks and easily dissolves in water.

Minerals of the phosphate, tungstate, and native element classes are much less common than others.

2. Glaciers, their geological role, distribution. Rocks formed as a result of the work of glaciers during the Ice Age.

Geological evidence suggests that in ancient times the glaciation of the Earth was significant. Over the past 500-600 thousand years, several large glaciations have occurred in Europe. Glaciers advanced from the Scandinavian region.

Currently, ice covers 10% of the land surface, 98.5% of the glacial surface is in the polar regions and only 1.5% is in high mountains. There are three types of glaciers: mountain, plateau and continental.

Mountain glaciers are formed high in the mountains and are located either on the peaks or in gorges, depressions, and various depressions. Such glaciers are found in the Caucasus, Urals, etc.

Ice is formed due to the recrystallization of snow. It has the ability to flow plastically, forming flows in the form of tongues. The movement of glaciers down slopes is limited by the altitude where solar heat is sufficient to completely melt the ice. For the Caucasus, for example, this height is 2700 m in the west, 3600 m in the east. The speed of movement of mountain glaciers is different. In the Caucasus, for example, it is 0.03-0.35 m/day, in the Pamirs – 1-4 m/day.

Glaciers of the plateaus formed in mountains with flat tops. The ice lies in an indivisible continuous mass. Glaciers in the form of tongues descend from it through the gorges. This type of glacier, in particular, is now located on the Scandinavian Peninsula.

Continental glaciers common in Greenland, Spitsbergen, Antarctica and other places where the modern era of glaciations is currently taking place. The ice lies in a continuous layer, thousands of meters thick.

The geological activity of ice is great and is determined mainly by its movement, despite the fact that the speed of ice flow is approximately 10,000 times slower than water in rivers under the same conditions.

Construction properties of glacial deposits. Moraine (coarse, heterogeneous, non-layered clastic materials) and fluvioglacial (fluvio-glacial) deposits are a reliable basis for structures of various types. Boulder loams and clays, which have experienced the pressure of thick layers of ice, are in a dense state and in some cases even over-compacted. The porosity of boulder loams does not exceed 25-30%. On boulder loams and clays, buildings and structures experience low settlement. These soils are weakly permeable and often serve as a waterproof barrier for groundwater.

Almost all types of moraine deposits have such high strength properties.

From a construction point of view, fluvioglacial deposits, although inferior in strength to moraine clayey soils, are a reliable foundation. For this purpose, various sandy, gravelly and clayey deposits of eskers and outwash are successfully used. Some exceptions are cover loams and band clays. Covering loams get wet easily. Band clays are quite dense, slightly permeable to water, but can be fluid under conditions of saturation with water.

Glacial deposits are successfully used as building materials (stone, sand, clay); The sands of eskers, kames and outwash are suitable for the construction of embankments and for the production of concrete. Boulders are a good building stone. There are examples of the use of boulders to make monolithic pedestals for monuments.

3. Geotechnical research for industrial and civil construction.

The main task of engineering-geological research for industrial and civil construction is to obtain information about the engineering-geological conditions of the territory, which include: relief, rocks and their properties, groundwater, geological and engineering-geological processes and phenomena, as well as forecasting changes in these conditions under the influence of human engineering activities.

Engineering geological studies are carried out sequentially,

in accordance with the design stage. The detail of research increases during the transition from one stage to another, and the methods of engineering and geological research also change.

At the initial stage of engineering surveys, the main type of engineering-geological research is engineering-geological survey, which makes it possible to assess engineering-geological conditions in a short time and at low cost.

During engineering-geological survey, rocks, their occurrence conditions, relief, groundwater, geological and engineering-geological processes are identified, studied and traced in the study area and depicted on an engineering-geological map.

It is important to understand that the composition and volume of engineering-geological research depends on the complexity of engineering-geological conditions, the design stage, the degree of exploration of the area and other factors.

Attention should be paid to the significant complexity of engineering-geological research in areas of karst development, landslides, buried valleys, where all research is carried out to a greater depth than during research in areas with more favorable engineering-geological conditions.

4. Laboratory methods for determining the deformation and strength properties of soils.

Strength soil is estimated by the maximum load applied to it at the moment of destruction (loss of continuity). This characteristic is called tensile strength R c MPa, or temporary compressive strength.

The strength of soils is affected by:

mineral composition

nature of structural connections

fracturing

degree of weathering

degree of softening in water, etc.

For non-rocky soils, another important strength characteristic is shear strength. Determining this indicator is necessary to calculate the stability of the foundations, i.e. bearing capacity, as well as for assessing the stability of soils in the slopes of construction pits, calculating soil pressure on retaining walls, etc.

Deformation properties characterize the behavior of soils under loads that do not exceed critical loads and do not lead to destruction. The deformability of soils depends both on the resistance and compliance of structural bonds, porosity, and on the ability of the materials composing them to deform. The deformation properties of soils are assessed by the deformation modulus E, MPa.

Soils determine the stability of buildings and structures erected on them, therefore it is necessary to correctly determine the characteristics that determine the strength and stability of soils during their interaction with construction objects.

Soil samples for laboratory research are selected from soil layers in pits in boreholes that are located on construction sites.

Soil samples are delivered to the laboratory in the form of monoliths or loose samples. Monoliths are samples of soil with an undisturbed structure. Such monoliths are selected in rocky and cohesive (silty-clayey) soils. The dimensions of the monoliths must be no less than the established standards. Thus, to determine the compressibility of soil, samples taken in pits must have dimensions of 20 × 20 × 20 cm. In monoliths of silty clay soils, natural moisture must be preserved. This is achieved by creating a waterproof paraffin or wax shell on their surface. In loose soils (sand, gravel), samples are taken in the form of samples of a certain mass. Thus, to carry out granulometric analysis of sand, it is necessary to have a sample of at least 0.5 kg.

In laboratory conditions, all physical and mechanical properties can be determined. Each characteristic of these properties is determined according to GOST, for example, natural moisture and soil density - GOST 5180-84, tensile strength - GOST 17245-79, granulometric (grain) and microaggregate composition - GOT 12536-79, etc.

Laboratory research today remains the main type of determination of the physical and mechanical properties of soils. A number of characteristics, for example, natural humidity, density of soil particles and some others are determined only in laboratory conditions and with fairly high accuracy. At the same time, laboratory soil studies have their drawbacks:

they are quite labor-intensive and time-consuming;

the results of individual analyzes, for example, determination of the modulus of total deformation, do not give sufficiently accurate results, which is due to improper selection of monoliths, improper storage, and low qualifications of the analysis performer;

Determining the properties of a soil mass based on the results of analyzes of a small number of samples does not allow one to obtain a correct idea of ​​its properties as a whole.

This is due to the fact that soils of the same type, even within the same massif, still have known differences in their properties.

5. Structure, texture, material composition of chemical and biochemical sedimentary rocks.

Rocks are natural mineral aggregates that are “born” in the earth’s crust.

According to their origin, they are divided into three types: igneous, sedimentary and metamorphic. In the earth's crust, igneous and metamorphic rocks occupy 95% of its total mass. Sedimentary rocks are located directly on the surface of the Earth, covering in most cases igneous and metamorphic rocks.

Sedimentary rocks. Any rock located on the earth's surface is subject to weathering, i.e. the destructive effects of water, temperature fluctuations, etc. As a result, even the most massive, durable igneous rocks are gradually destroyed, forming fragments of various sizes and disintegrating into the smallest particles.

Destruction products are transported by wind, water and, at a certain stage of transport, are deposited, forming loose accumulations or sediments. Accumulation occurs at the bottom of rivers, seas, oceans and on the surface of the land. From loose accumulations (sediments) various sedimentary rocks are formed over time.

Sedimentary rocks make up the uppermost layers of the earth's crust, covering rocks of igneous and metamorphic origin with a kind of cover. Despite the fact that sedimentary rocks make up only 5% of the earth's crust, 75% of the earth's surface is covered with these rocks, and therefore construction is carried out mainly on sedimentary rocks. Engineering geology pays the greatest attention to these rocks.

Sedimentary rocks are usually divided into three main groups:

1) clastic;

2) chemical origin (chemogenic);

3) organogenic, resulting from the vital activity of organisms.

This division is somewhat arbitrary, since many rocks are of mixed origin, for example, some limestones contain material of an organogenic, chemical and clastic nature.

Chemogenic rocks are formed as a result of the precipitation of their aqueous solutions of chemical precipitation. This process occurs in the waters of the seas, continental drying basins, salty springs, etc. These rocks include various limestones, calcareous tuff, dolomite, anhydrite, gypsum, rock salt, etc. A common feature of these rocks is their solubility in water and fracturing.

The most common rocks are limestones, which in their origin can also be clastic or organogenic.

Organogenic (biochemogenic) rocks are formed as a result of the accumulation and transformation of animal and plant remains, are characterized by significant porosity, many dissolve in water, and are highly compressible. Organogenic rocks include limestone-shell rock and diatomite.

6. Inflow of pressure water into a perfect well.

The water located in the upper part of the earth's crust is called groundwater. The science of groundwater, its origin, conditions of occurrence, laws of movement, physical and chemical properties, connections with atmospheric and surface waters is called hydrogeology.

There are several classifications of groundwater, but there are two main ones. Groundwater is divided according to the nature of its use and the conditions of occurrence in the earth's crust. The first includes household and drinking water, technical, industrial, mineral, thermal. The latter include: perched water, groundwater and interstratal water, as well as water from cracks, karst, and permafrost. For engineering and geological purposes, it is advisable to classify groundwater according to hydraulic criteria - free-flow and pressure.

Interlayer pressure waters. These waters are located in aquifers between aquitards. They can be non-pressure and pressure (artesian).

Interstratal non-pressure waters are relatively rare. They are associated with horizontal aquifers filled with water completely or partially.

Pressure (artesian) waters are associated with the occurrence of aquifers in the form of synclines and monoclines. The area of ​​distribution of confined aquifers is called an artesian basin.

Inflow of pressure water to water intake structures. Water intakes are structures with the help of which groundwater is captured (withdrawn) for water supply, drained from the construction site or simply for the purpose of lowering groundwater levels. There are different types of underground water intake structures: vertical, horizontal, radial.

Vertical water intakes include boreholes and shaft wells, horizontal ones include trenches, galleries, adits, and radial water intakes include drainage wells with water receiving filter beams. The type of structure for underground water intake is selected on the basis of a technical and economic calculation, based on the depth of the aquifer, its thickness, the lithological composition of the aquifer and the planned water intake capacity.

Water intakes consisting of one well, well, etc. are called single, and those consisting of several are called group.

Water intake structures that tap the aquifer to its full capacity are perfect, and those that do not tap the aquifer to its full capacity are imperfect.

The removal of groundwater from construction sites or the reduction of their levels can be carried out temporarily, only for the period of construction work or for almost the entire period of operation of the facility. Temporary water removal (or lowering the level) is called construction water intake, and in the second case - drainage.

Water intake wells. Wells and trenches, the bottom of which reaches aquicludes, are called perfect; if the bottom is located above the aquiclude, then imperfect. The water level in the well before pumping is called static, and the level reduced during pumping is called dynamic.

If water is not pumped out of the well, then its level is in the same position as the surface of the ground flow. When water is pumped out, a depression funnel appears and the water level in the well decreases. The productivity of the well is determined by the flow rate. The flow rate of a well is understood as the amount of water it can produce per unit of time. When pumping water in an amount greater than the flow rate, i.e. more than what flows into the well from the aquifer per unit time, the level drops sharply. The well may remain without water for some time.

The influx of water (flow rate) to a perfect well is determined by the formula

Q = π k f [H 2 -h 2 )/lnR-lnr]

Where r– radius of the well, m.

In an imperfect well, water enters through its walls and bottom. This complicates the calculation of inflow. The flow rate of such wells is less than the flow rate of perfect wells. When pumping, water enters the well only from a part of the aquifer, which is called the active zone N 0 . The depth of the active zone is taken to be 4/3 of the height of the water column in the well before pumping. These provisions allow the flow rate for an imperfect well to be calculated using the Dupuis formula, as interpreted by Parker:

Q = 1.36 k f [H 2 -h 2 )/lnR-lnr]

A well releases water in the volume of its maximum flow only if neighboring wells are located from it at a distance of at least two radii of influence.

List of used literature. rock classification takes into account conditions their education, which predetermine the structure and,... marble), or from many complex silicates. Main rock-forming minerals represented by quartz, feldspars, micas...

Minerals are classified according to their chemical composition and crystal structure into the following groups:

1) native elements;

2) sulfides and sulfosalts;

3) halogen compounds (halides);

4) oxides;

5) oxygen salts (carbonates, sulfates, tungstates, phosphates, silicates).

Below we will consider the minerals of these groups, included in the mineralogy course program for students of metallurgical faculties of higher educational institutions.

Native elements

The earth's crust contains no more than 0.1% (by mass) of native elements (83 minerals). Their extraction is associated with significant difficulties, and therefore many of them are especially highly valued and, being standards of human labor, are used in the gold reserves of countries as collateral for national currency in international trade. Genetically related to magma crystallization processes (Pt, diamond, graphite), hydrothermal (Au) and sedimentary (S) processes. Native iron is often of cosmic origin.

Native metals are characterized by extremely high ductility, metallic luster, malleability, thermal and electrical conductivity, caused by metallic bonds in the crystal lattice.

High densities are also characteristic. They are possessed by the heaviest minerals: nevyanskite (up to 21.5 g/cm3) and syssertskite (up to 22.5 g/cm3).

In addition to native metals (Ru, Rh, Pd, Ag, Os, Ir, Pt, Au, Fe, Cu, Ni, Hg), there are also native metalloids (As, Sb, Bi) and nonmetals (S, Se, Te, C) .

Gold, Au. Name from lat. "Soil" - the sign of the sun among alchemists. Absolutely clean, so-called. "Spongy" gold is rare. It forms a continuous series of solid solutions with silver (kustelite contains up to 20% Au; electrum - over 20% Au), from which gold turns white, as well as with copper (cuproaurid contains up to 20% Cu), the admixture of which gives gold a reddish tint. Bismuthaurite contains up to 4% Bi; porpecite - up to 11% Pd and up to 4% Ag.

A gold nugget weighing more than 70 kg. At the Harvard Museum (Natural History). Photo: Olivier Chafik

Gold crystals (octahedrons, dodecahedrons and cubes) are rare. Characterized by irregularly shaped grains embedded in quartz. Primary gold deposits are formed by the movement of thermal waters through cracks and pores in quartz. Often precipitates from solutions along with sulfides. When bedrock deposits are weathered, water carries grains of gold into streams and rivers, at the bottom of which placers of gold are formed, mined by dredges.

Polixenes, Pt. Name from Greek. "poly" - many, "xenos" - alien (meaning the presence of numerous impurities in Pt). In technology and everyday life it is called platinum (from the Spanish “plata” - silver), i.e. similar to silver, "silver". Contains up to 30% Fe, which gives the mineral magnetism (up to 14% Cu; up to 7% Pd, up to 7% Ir; up to 4% Ro, up to 6% Ni).

Pt crystallizes as fine grains in ultramafic magmas. Characteristic features: steel-gray color, metallic luster, high density. It dissolves only in heated aqua regia, which makes it possible to distinguish Pt from similar silver. Unusually plastic: up to 500 km of wire can be made from 1 g. The presence of iridium in Pt increases its hardness to 7. It is used as a catalyst in chemistry, for the manufacture of chemical crucibles, thermocouples.

Iron, Fe. Native iron can be telluric (i.e. terrestrial) and meteoritic (i.e. cosmic). Native cast iron (telluric iron) is formed by the interaction of ferruginous magma with coal, graphite, or during underground fires of coal seams in contact with iron ore. Meteoric iron (ferrite) usually contains inclusions of troilite (FeS), monsonite SiC and cohenite (Fe3C). In the vast majority of cases, it contains a lot of Ni (up to 48%), which is distributed unevenly in meteorites, concentrating in stripes intersecting in thin section at an angle to each other. This alternation of light and dark stripes (Widmanstätt structure) is characteristic of meteoritic iron and is especially well revealed when etching sections with a weak alcohol solution of HN03. Meteoric iron is occasionally observed in the form of regular cubes (hexahedral iron) and octahedrons (octahedral iron). Usually in the form of melted masses of unrounded shape with characteristic finger-shaped depressions on the surface. The so-called “Pallasian iron” contains inclusions of olivine (MgFeSiO4). Mesosiderite contains iron inclusions in a mass of silicates. The last two varieties of meteorite iron belong to the so-called stony-iron meteorites.

Sulfur, S. Characterized by diamond luster, yellow color, fragility; burns with a blue flame, spreading the smell of sulfur dioxide. Formed during weathering of gypsum CaS04. 2 H2O and sulfides with the participation of microbes, as well as during the oxidation of hydrogen sulfide released from volcanoes: H2S + O2 = 2H2O + S. Used for the preparation of gunpowder, for the vulcanization of rubber, in medicine and chemistry.

Deposits: o. Sicily (Italy), Central Asia (Shor-Su) and in the Volga region (Tver region).

Graphite, S. Name from Greek. "grapho" - write; This refers to the ability of graphite to leave a black line on paper. It is formed during crystallization from magma at high temperatures and low pressures, as well as during natural coking of coals at their contacts with magma.

Varieties: cryptocrystalline graphite and amorphous shungite. Graphite is greasy to the touch and writes on paper. It differs from similar molybdenite in its blacker color and less shine.

Used for the manufacture of electrodes and refractory blocks, graphite blocks for nuclear reactors.

Deposits: o. Ceylon, o. Madagascar, Australia.

Almaz, S. Name from Greek. "adamas" - irresistible (meaning the extraordinary hardness of the diamond). Crystallizes from ultrabasic magma in the form of octahedra at pressures above 10 GPa. and temperatures of about 2000 °C. Diamond probably crystallizes from magma first at great depths, after which it is carried by liquid magma to the surface through the vents of giant volcanoes. The remains of such volcanic pipes (diatremes), filled with ultrabasic magma, weathered for 140 - 150 million years, are found in our time in Yakutia (Russia) and South Africa.

A mixture of the remains of olivine with the products of its decay, which is a greenish-blue clay, is called kimberlite.

Sulfides

The earth's crust contains no more than 0.15% (by mass) of minerals of this group (230 minerals). From a chemical point of view, these compounds are salts of hydrogen sulfide acid. There are both sulfides of strictly stoichiometric composition (FeS2, CuFeS2, etc.) and compounds in which the sulfur content varies within certain limits (polysulfides, for example FeSx, where x = 1.0.1 - 1.14).

Ionic crystal lattices are characteristic. Most sulfides are heavy, soft, and shiny. They have high electrical conductivity. In most cases, of hydrothermal origin, sometimes a product of crystallization of sulfide magma. During weathering in the oxidation zone, sulfides transform first into sulfates, and then into oxides, hydroxides, and carbonates.

Sulfides represent the ore base of non-ferrous metallurgy and are the raw material for the production of sulfuric acid. Since sulfur makes steel red-brittle, the presence of sulfides in iron ores reduces their quality. Before blast furnace smelting, pulverized iron ores are subjected to agglomeration at sintering factories. During sintering, it is possible to remove up to 99% of sulfide sulfur from the ore.

Pyrite, FeS2. Name from Greek. "pir" - fire (gives a stable spark when struck by a metal object; used to produce a spark in ancient guns). Synonyms: sulfur pyrite, iron pyrite. The rhombic variety is called marcasite. Characteristic features are straw-yellow color, black streak, cubic, pentagon-dodecahedral and octahedral appearance of crystals, streaked edges oriented perpendicular to each adjacent face. The most important raw material for the production of sulfuric acid; deposits: Ural (Russia), Rio Tinto (Spain).

Pyrrhotite, FeS. Name from Greek. "pyrrhos" - reddish. Synonym: magnetic pyrite. Troilite is a stoichiometric variety found in meteorites. Typically, pyrrhotite contains slightly more sulfur (FeSx, where x = 1.01 - 1.14). Characterized by a metallic luster, bronze-yellow color, and magnetism. Usually in association with other sulfides hydrothermal. Raw materials for the production of sulfuric acid. Harmful impurity in iron ores.

Arsenopyrite, FeAsS. Synonyms: poisonous arsenic pyrite, mispickel. Danaite and glaucodotus are varieties containing up to 9 and 22% Co, respectively. Characteristic: metallic luster, tin-white color, elongated columnar, needle-shaped crystals of prismatic appearance. Hydrothermal. Ore for As and Co. Numerous deposits in the Urals and Siberia, Boliden (Sweden). The presence of arsenopyrite, orpiment (As2S3), realgar (AsS), scorodite (FeAsO4. 2H2O) and other arsenic minerals in iron ores is unacceptable, since arsenic is a strong poison, which prevents the manufacture of pots, cans, spoons, knives and forks from steel , containing at least traces of arsenic. The manufacture of rails and beams from such steel is also undesirable, since in the future all scrap metal in the country will gradually become contaminated with arsenic. In Ukraine, Kerch brown iron ores contain up to 0.1% As in scorodite.

Chalcopyrite, CuFeS2. Name from Greek. "chalcos" - copper; "feast" - fire. Synonym: copper pyrite. The cubic variety is called talnakhite. Usually found in solid masses and grains. Hydrothermal. Characteristic: metallic luster, greenish-yellow color with bright variegated tarnish, black streak. The most important copper ore.

Bornite, Cu5FeS4. The name is given in honor of the Austrian mineralogist Joachim von Born (1742 - 1791). Synonyms: mottled copper ore, peacock ore. It is always found in solid masses and in the form of interspersed grains. Hydrothermal. Characteristic: metallic luster, blue tarnish. When scratched with a steel knife, the true copper-red color of the mineral is revealed. Valuable copper ore. Deposits: Butte (Montana, USA), Morococha (Peru), Braden (Chile), Neldy (Kazakhstan).

Galena, PbS. Name from lat. "galena" - lead ore. Synonym: lead sheen. The crystals are cubic in shape. Characteristics: strong metallic luster, perfect cube cleavage, lead-gray color, softness. The most important lead ore. Deposits: Turlanskoye (Turkmenistan), Sadonskoye (North Caucasus Russia), Dalnegorsk (Far East, Russia), Leadville (Colorado, USA), Broken Hill (Australia), Mississippi River Valley in Missouri (USA). The presence of galena in iron ores, as is the case in Altai, is unacceptable and completely depreciates the value of the ore. Lead is easily reduced in a blast furnace, enters the seams of brickwork in the flange and the hearth, which leads to the floating of bricks, rapid destruction of the masonry and to severe accidents associated with breaks in the hearth and leakage of cast iron from the blast furnace through its foundation and the walls of the hearth.

Sphalerite, ZnS. Name from Greek. "sphaleros" is deceptive (sphalerite is often confused with other minerals). Synonym: zinc blende.

Varieties: black marmatite and christophite, brown prshibramite, light - cleiophane. Hexagonal ZnS is called wurtzite. Hydrothermal. Characteristic: metallic luster, tetrahedral appearance of crystals, which differs from wolframite (MnFeWО4), which is similar in color. The most important zinc ore. Deposits: Pribram (Czech Republic), Santader (Spain), Joplin (Missouri, USA). The presence of sphalerite in iron ores is unacceptable. In a blast furnace, zinc and zincite vapors condense in the seams of the shaft masonry, which leads to swelling, rupture of the sealed furnace casing and serious accidents.

Molybdenite, MoS2. Name from Greek. "molybdos" - lead (the presence of lead in the mineral was assumed; molybdenum was discovered later and named after the name of the mineral). Synonym: molybdenum luster. Characteristic: perfect cleavage in leafy scaly aggregates, strong metallic luster, low hardness (scratchable with a fingernail), writes on paper. Lighter than graphite. Hydrothermal. The most important ore on Mo. Deposits: Tyrnyauz (North Caucasus, Russia), Climax (Colorado, USA).

Cinnabar, HgS. The name comes from the Indian "dragon's blood" (associated with the intense red color of the mineral). Synonym: cinnabarite. In cryptocrystalline masses called “liver ore”, and in the form of spreads and coatings. Hydrothermal. Easily distinguished by color and high density. The most important ore for mercury. Deposits: Nikitovka (Donbass, Ukraine), Almaden (Spain), Idria (Yugoslavia), New Idria and New Almaden (California, USA).

Antimonite, Sb2S3. Name from lat. "antimonium" - antimony.

Synonyms - antimony shine, stibnite. Usually in the form of prismatic, needle-shaped crystals with vertical shading with a bright metallic luster. Perfect cleavage. Hydrothermal. The most important ore for antimony, deposits: o. Shikoku (Japan), Razdolninskoye (Krasnoyarsk Territory, Russia).

Halide compounds

The Earth's crust contains about 0.5% (by mass) of halogen compounds, which are of hydrothermal or sedimentary origin. Fluorite is often found in pegmatite veins. From a chemical point of view, these minerals are salts of acids: HF, HI, HBr, HCI. Characteristics: glassy luster, low density, solubility in water. Halide compounds have ionic lattices.

Metallurgy uses large quantities of fluorite to liquefy slags. Halide compounds are widely used in chemistry, agriculture (fertilizers), and the food industry.

Fluorite, CaF. Name from Italian. "fluore" - leak (fluorite additives liquefy metallurgical slags). Synonym: fluorspar. Hydrothermal or magmatic (in pegmatite veins). It occurs in the form of cubic and octahedral crystals, or in solid granular masses. Colorless or colored green, purple. Fluorescence is characteristic, i.e. glow in x-rays. Perfect cleavage along the octahedron.

Halite, NaCl. Name from Greek. "halos" - sea (meaning the production of salt by evaporation of sea water containing 35 g of salts in 1 liter, including 78% NaCI, 11% MgCl2, the rest MgSO4, CaSO4, etc.). Synonym: rock salt. Characterized by solubility in water and very perfect cube cleavage. Often in the form of cubic crystals, or in solid masses. It is usually transparent and colorless, but impurities color halite gray, yellow, red and black. It is used as an ore for sodium, as well as for the preparation of electrolytes in the food industry. Deposits: Suez (Egypt), Wieliczka (Poland), Punjab (India), Slavyanovskoye (Donbass), Solikamskoye (Urals).

Silvin, KCI. Named after the Dutch doctor Sylvia de la Bache. Sedimentary. Usually in the form of solid granular masses, less often in the form of cubes. Colorless, milky white, pink and red. Paragenesis with halite is typical. Aqueous solutions have a bitter taste. It is used in agriculture as a potash fertilizer, as well as in the chemical industry. Deposits: Solikamsk (Ural), Stasfurt (Germany), New Mexico (USA).

Carnallite, MgCl2. KCl. 6H2O. Named after the German engineer von Carnall. Usually in solid or granular aggregates. Bitter taste. It gradually spreads out, absorbing water from the atmosphere. It differs from similar red halite in that it creaks when drilled with a steel object. Characteristics: red color, greasy sheen, bitter taste, lack of cleavage. Used for the production of magnesium, as potash fertilizer. Deposits: Solikamskoye (Ural), Starobinskoye (Belarus), Prikarpatskoye (Ukraine).

Oxides

The general characteristics of the group are given in table. 4.1. The earth's crust contains up to 17% (by mass) oxides. The most common are quartz (12.6%), iron oxides and hydroxides (3.9%), oxides and hydroxides of AI, Mn, Ti, Cr. Let us recall here that the bulk of iron ore and manganese ores are of sedimentary origin. Minerals of the oxide group are the ore base of ferrous metallurgy. The most important ore minerals of iron and manganese ores: hematite (Fe2O3), magnetite (Fe3O4), brown ironstone (Fe2O3. H2O), pyrolusite (MnO2), braunite (Mn2O3), hausmannite (Mn3O4), psilomelane (MnO2. MnO. n H2O) , manganite (MnO2. Mn(OH)2.

Crystal lattices of oxides are characterized by ionic bonding. Oxides of Fe, Mn, Cr, Ti have a semi-metallic luster and dark color. These minerals are opaque. A characteristic property of magnetite (Fe3O4) and ilmenite (FeO. TiO2) is their magnetism.

Magnetite, Fe3O4. Named after a mineral deposit in the province of Magnesia (Greece). Synonym: magnetic iron ore. Important iron ore. Magnetite in its pure form (without waste rock) contains up to 72.4% Fe. The magnetite lattice contains di- and trivalent iron: FeO. Fe2O3. Due to isomorphism, the Fe2* and Fe3* positions can be occupied by cations of the corresponding valency that are similar in size. This gives a huge range of magnetite-based minerals: calcium magnetite (Ca; Fe)O. Fe2O3, magnetite (Mg, Fe)0. Fe2O3, magnesioferrite MgO. Fe2O3. Chromomagnetite FeO. (Fe, Cr)2O3, aluminum magnetite FeO. (Fe, A1)2O3. Titanomagnetites can contain Ti in the crystal lattice of magnetite (TiO. Fe2O3 - ulvöspinel) or in the composition of ilmenite (FeO. TiO2), with which magnetite co-crystallized. It is clear that mechanical separation of Ti from Fe is possible only in ilmenite.

In the oxidation zone, magnetite gradually turns into hematite under the influence of atmospheric oxygen. The oxidation products of magnetite in nature are called semi-martites and martites.

Although in technology ferrous monoxide (FeO, wüstite) is produced in the blast furnace process in the millions of tons, in nature it is extremely rare (FeO, iocyte). Thus, only higher iron oxides are present in the oxidation zone: magnetite (Fe3O4), hematite (Fe2O3) and hydroxides (Fe2O3 nH2O).

Most often, magnetite forms solid granular masses of black color. Sometimes it occurs in the form of regular octahedral crystals. It differs from similar chromite in its black streak and strong magnetism.

Table 4.1 - Oxides

Hematite, a- Fe2O3. The name is associated with the red color of the mineral and its features (“hematikos” - Greek - bloody). Synonym: red iron ore. In nature and technology, there is also a tetragonal variety of this oxide - maghemite (oxymagnetite), g-Fe2O3.

It occurs as continuous dense cryptocrystalline masses or as banded ore, in which the ore material is located among bands of quartz gangue. The crystals have a lamellar, rhombohedral appearance. Color cherry red, iron black, steel gray. The streak is cherry red. Sintered varieties with a smooth red surface are called red glass head. A coarse-crystalline variety of dark steel color - iron luster (specularite). Under the influence of rock pressure, leafy, scaly varieties of hematite appear - iron mica, iron sour cream. Most of the hematite ore mined is Precambrian sedimentary ore. As already indicated, hematite and martite ores currently account for up to 90% of the world's cast iron production. In its pure form it contains up to 70% Fe. The largest deposit is Krivoy Rog, Ukraine.

Goethite, Fe3O4. H2O. Named after the German poet Goethe. There are a number of brown ironstones that differ from each other in the amount of hydration water: hydrohematite Fe2O3.

In this series, only goethite has its own fixed x-ray pattern. Hydrogoethite, limonite, xanthosiderite and limnite are solid solutions of water in goethite; hydrohematite is a solid solution of water in hematite. Turyite is a mechanical mixture of hydrohematite and goethite. The true formula of brown iron ore can be determined by calcining its sample to a constant mass. We also note the sintered variety of brown iron ore - brown glass head, as well as transparent lepidocrocite mica (FeO. OH). The overwhelming mass of brown iron ore of sedimentary origin has an oolitic structure. Important iron ore. In its pure form it contains up to 66.1% Fe.

Chromite, (FeO Cr2O3). Synonym: chromium iron ore. Igneous. Varieties: aluminum chromite (FeO. (Cr, Al)2O3, magnochromite (Fe., Mg)0. Cr2O3, chromopicotite (Fe, Mg)0. (Cr, Al)2O3. Paired with a light coil Mg6 (OH)3 chromite gives structures that look like the wing of a hazel grouse ("chromite - hazel grouse"). It is usually found in the form of continuous granular aggregates or individual disseminated grains. It differs from similar magnetite by its brown streak and lack of magnetism. The most important ore for chromium. Deposits: Kempirsai (Aktobe region) , Saranovskoe (Northern Urals), Zimbabwe (Africa).

Ilmenite (FeO. TiO2). The name comes from the Ilmen Mountains (Southern Urals). Synonym: titanium iron ore, picroilmenite (Mg, Fe)O. TiO2. The shape of the crystals is thick-tabular and rhombohedral. It differs from similar dark hematite in its weak magnetism and brown-black feature. Igneous: Eksrsund (Norway), Iron Mountain (Wyoming, USA), Akkard Lake (Quebec, Canada).

Pyrolusite (MnO3). Name from Greek. “pyro” - fire and “luzis” - destroyed (pyrolusite additives destroy the colored colors of glass). Well-cut pyrolusite is called polyanite. Sedimentary. Characteristics: soft, oolitic, earthy, black, stains your hands. The most important manganese ore, widely used in the smelting of iron and steel, ferroalloys. Deposits: Nikopolskoye (Ukraine), Chiaturskoye (Georgia).

Brownite (Mn2O3). Name in honor of the German chemist K. Braun. The varieties contain up to 8% SiO2 in the form of a finely dispersed mechanical impurity and up to 10% Fe, which is included in the crystal lattice of the mineral (Mn, Fe)2O3. Most often observed in the form of glued granular aggregates. Noticeable cleavage. It differs from similar pyrolusite in its brownish color and increased hardness.

Corundum (A12O3). The name is of Indian origin. Usually in barrel-shaped, columnar, pyramidal crystals of bluish, yellow-gray, reddish color. Transparent crystals of corundum are colored in different colors and are its precious varieties: leucosapphire (colorless), ruby ​​(red), sapphire (blue), oriental topaz (yellow), oriental emerald (green) and oriental amethyst (purple). All of the listed varieties of corundum have a hardness of 9, second only to diamond. In this regard, oriental topaz, amethyst and emerald are valued higher than ordinary topaz (tv. 8), amethyst (tv. 7) and emerald (tv. 7.5 - 8). Easily identified by color, crystal shape and high hardness. It is widely used in the abrasive industry, where grinding wheels and grinding powders are made from corundum powder.

Aluminum hydroxides gibbsite Al(OH)3, hydragillite Al(OH)3, boehmite (AlO OH) and diaspores (AlO. OH) form the basis of bauxite - a valuable raw material used for aluminum smelting - or in the production of refractories. Bauxite, brick-red or red-brown in color, differs from similar brown iron ore by its red line, and from red clays by the fact that it does not form a plastic mass with water. Bauxite deposits: Krasnaya Shapochka, Severouralsk, Ivdelsk, Alapaevka (all in the Urals),

Quartz (SiO2). Name from it. "kuerertz" - transverse ore (meaning quartz veins, usually located along cracks across the direction of rock layers). Quartz crystals have the appearance of pseudohexagonal prisms and bipyramids with characteristic transverse shading of the prism faces. The earth's crust contains up to 13% (by mass) quartz, which is the most common mineral on earth. The origin is magmatic and hydrothermal. Easily recognized by the shape of the crystals, conchoidal fracture and lack of cleavage, high hardness.

Varieties of quartz: transparent colorless - rock crystal, transparent: yellow - citrine, purple - amethyst, smoky - rauchtopaz (smoky quartz). Black opaque - morion.

The cryptocrystalline opaque variety (SiO2) with a matte surface and waxy luster is called chalcedony. Usually white, sintered, amorphous, hardness 7, opaque, no cleavage. Varieties, carnelian (red), sarder (brown), sapphirine (milky blue), plasma and chrysoprase (green), heliotrope (green with red spots). Chalcedony usually has a zonal structure; however, the porosity of the zones is different. When natural or technical aqueous solutions pass through the pores, these zones become stained. This is how agate is obtained, i.e. zonally colored chalcedony.

Solid amorphous quartz hydrogel (SiO2.H2O) is called opal. Its transparent varieties are precious. Opal is recognized by its enamel-like fracture and high hardness.

Precious varieties of quartz, chalcedony, agate and opal are widely used in jewelry. Quartz is also used in industry: in optics, for the manufacture of piezoquartz plates for pickups, in precision mechanics for the manufacture of support bearings and thrust bearings, for the manufacture of chemical glassware, as well as in fireproof and glass production.

Carbonates, sulfates, tungstates, phosphates

General characteristics of the groups are given in table. 4.2. Carbonates, making up about 1.7% of the Earth's crust, are sedimentary or hydrothermal minerals. From a chemical point of view, these are salts of carbonic acid - H2CO3. Carbonates have ionic crystal lattices; characterized by low densities, glassy luster, light color (except for copper carbonates), hardness 3-5, reaction with dilute HCl. Carbonates are widely used in the iron and steel industry as a flux and as a raw material for the production of refractories and lime.

The earth's crust contains 0.1% (by mass) of sulfates, which are mainly of chemical sedimentary origin and are salts of sulfuric acid H2SO4. Usually these are soft, light, light minerals. Outwardly, they are similar to carbonates, but do not react with HCl. Sulfates are used in the chemical and construction industries. They are an extremely harmful impurity in iron ores, since during agglomeration it is possible to remove no more than 60 - 70% of sulfate sulfur into the gas phase.

Phosphates are of igneous (apatite) and sedimentary (phosphorite) origin. Tungstates are more common in hydrothermal and pegmatite veins.

Calcite, CaCO3. Name from Greek. "calc" - burnt lime.

Synonym: lime spar. Sedimentary organogenic, hydrothermal. Crystals in the shape of rhombohedrons. Perfect cleavage along the rhombohedron. Boils under the influence of dilute HCl in the cold. Varieties: transparent, colorless - Iceland spar, rhombic white - aragonite. The strata of sedimentary rocks consist mainly of calcite: chalk, limestone, marble. Lime tuff - travertine - is also made of calcite.

The iron and steel industry consumes millions of tons of limestone as a flux. In addition, limestone is burned into lime in the construction industry. Iceland spar is used in optics to make polarizers.

Magnesite, MgCO3. Named after the Greek province of Magnesia. Synonym: magnesium spar. The shape of the crystals is rhombohedral with perfect cleavage along the rhombohedron. In most cases, it occurs in the form of snow-white granular aggregates with a conchoidal fracture (“amorphous” magnesite) and in gray elongated grains. Hydrothermal. An important raw material for the production of fire bricks and refueling powders. The use of dolomitized limestone improves the quality of sinter and pellets and reduces the viscosity of blast furnace slag. Deposits: Satkinskoye (Russia), Veitch (Austria), Liao Tong and Shen-Kin (Northeast China), Quebec (Canada).

Malachite, CuCO3 × Cu(OH)2. Name from Greek. "malakhe" - malva (meaning the green color of the leaves of the mallow). Azurite, 2CuCO3 × Cu(OH)2. The name comes from the Persian "lazvard" - blue. Sintered, earthy, concentrically shell-like. Boils under the influence of dilute HCl. Used as decorative ornamental stones, ores for copper.

Siderite, FeCO3. Name from Greek. a word for iron. Synonym: iron spar. Usually in granular yellowish-white, brownish masses. Reacts with cold HC1, a drop of which turns green. Hydrothermal. Siderite contains up to 48.3% Fe and is used as iron ore. Place of Birth:

Bakalskoye (Southern Urals), Kerchenskoye (Ukraine).

Rhodochrosite, MnCO3. Name from Greek. "Rodon" - rose and "khros" - color. Synonym: manganese spar. Usually in the form of granular aggregates of pink, crimson color, with a white streak. Reacts with cold HCl. Hydrothermal. Used as manganese ore. Deposits: Chiaturskoe (Georgia), Polunochnoe (Northern Urals), Obrochishche (Varna, Bulgaria).

Gypsum, CaSO4 × 2H2O. Name from Greek. a term referring to fired gypsum and plaster. Varieties: fibrous gypsum - selenite; lamellar, transparent - “Maryino glass”; fine-grained dense massive variety - alabaster. Technical alabaster (CaSO4 × 0.5H2O) is obtained by firing gypsum. Characteristic are tabular crystals with perfect cleavage, intergrowth twins and others resembling roses. It differs from a similar anhydride in lower hardness. From calcite - lack of reaction with HC1. It is used in construction, chemistry and medicine, as well as for the manufacture of sculptures and art objects. Deposits: on the western slope of the Urals, Artemovskoye (Donbass) and in many other areas.

Barite, BaSO4. Name from Greek. "baros" - heaviness. Synonym for heavy spar. It occurs in the form of white, gray tabular crystals with perfect cleavage, and more often in the form of granular aggregates. Easily distinguishes from carbonates by its high density and lack of reaction with HC1; from other sulfates and from silicates - by density. It is used in the oil industry for cementing loose rocks in the walls of wells, in chemistry, and also for the manufacture of “barite plaster” that absorbs X-rays in laboratories and hospitals. Harmful impurity in iron ores. Deposits: in Georgia, Turkmenistan, Center. Kazakhstan and the Southern Urals.

Wolframite, (Mn, Fe)WO4. Name from it. “wolf foam” (the admixture of this mineral with tin ores produces wolf-hair-colored slag when smelted). Synonym: Wolf. Usually in the form of thick tabular and prismatic crystals with shading on the edges or in the form of granular aggregates. Characterized by a brownish-black color, brown streak and high density. The most important ore for tungsten. It is used in metallurgy for the production of hard alloys and high-speed tools, as well as in the electrical industry for the manufacture of incandescent filaments in electric lamps and X-ray tubes. Deposits: Yunan (China), on the Malay Peninsula and Burma, Cornwall (England), Beira Bakes (Portugal), Tana (Bolivia), Boulder (Colorado, USA).

Scheelite, CaWO4. Named after the Swedish chemist Scheele (1742 -1786). It is found in bipyramidal, pseudooctahedral crystals, as well as in the form of irregularly shaped yellowish inclusions with a diamond luster and obvious cleavage. The second most important tungsten ore. Deposits: Wed. Asia, Saxony, Zinnwald (Czech Republic), Piedmont (Italy), Andalusia (Spain), Huancaya (Peru), states of California, Arizona, Nevada, Connecticut (USA).

Apatite. Name from Greek. “apatao” - deceiving (looks like precious beryl (emerald) and tourmaline, which made diagnosis difficult). The most common fluorapatite is Ca53F or 3 × CaF2, but chlorapatite is also found - Ca53Cl or 3 × CaCl2. It occurs in the form of hexagonal prisms and needles in pale green, emerald green and blue. The fracture is uneven and conchoidal. It is also widely distributed in the form of granular, dense white masses. It differs from precious emerald and aquamarine in less hardness (apatite does not scratch glass).

Together with vivanite Fe32 × 8H2O ("blue earth"), apatite is usually the main carrier of phosphorus in iron ores; the presence of these minerals in iron ore complicates metallurgical processing and depreciates the value of the ore, since phosphorus makes steel cold-brittle.

The classification of minerals by chemical composition is based on the chemical composition and crystal structure

Since each mineral is a specific chemical compound with a characteristic structure, the modern classification of minerals is based on chemical composition and crystal structure. There are ten classes of minerals: silicates, carbonates, oxides, hydroxides, sulfides, sulfates, halides, phosphates, tungstates
and molybdates, native elements.

The relationships between the quantities of mineral species by class and their content in the earth's crust are given in Table -1. As can be seen from this table, the most common are silicates and aluminosilicates, as well as oxides and carbonates, which make up almost 94% of the earth’s crust, which corresponds to the general occurrence of chemical elements in nature (see table 2. Systematics of all chemical elements of the earth’s crust according to their quantitative role in the composition of minerals was carried out by A.S. Povarennykh (see table-3).

For the most common silicate minerals in nature, classification according to structural characteristics is widely used: island - olives, garnet, sillimanite, melinite; ring - beryl; chain-pyroxenes; ribbon-amphiboles, hornblende; sheet-micas, chlorites, framework-feldspars, feldspathoids. The characteristics of the main rock-forming minerals are given below.

Table 1. Distribution of mineral species between individual classes of minerals and their content in the earth’s crust

Silicates. The most numerous and widespread class of minerals. Silicates have a complex chemical composition
and isomorphic replacement of some elements and complexes of elements with others. Common to all silicates is the presence in the anionic group
silicon-oxygen tetrahedra 4- in various combinations. The total number of mineral types of silicates is about 800. In terms of prevalence, silicates account for more than 75% of all minerals in the lithosphere.

Silicates are the most important rock-forming minerals, which make up the bulk of rocks (feldspars, mica, hornblende, pyroxenes, olivine, chlorite, clay minerals). The most common minerals in nature are the feldspar group of minerals.

2. Carbonates. Carbonates are salts of carbonic acid. This is a large group of minerals, many of which are widespread. They are most widespread on the earth's surface and in the upper part of the earth's crust. Carbonates are found mainly in sedimentary and metamorphic (marble) rocks. Most carbonates are anhydrous and are simple compounds, mainly Ca, Mg and Fe with a complex anion 2-. Typical representatives of the class of carbonates are calcite, dolomite, malachite, siderite, and magnesite.

3-4.Oxides and hydroxides. Oxides are compounds of elements with oxygen; hydroxides also contain water. In the earth's crust, the share of oxides and hydroxides accounts for about 17%. The most common minerals of this class are the oxides of Si, Al, Fe, Mn, Ti, while the mineral quartz SiO2 is the most common mineral on earth (about 12%). In the crystal structures of minerals of the oxide class, metal cations are surrounded by oxygen anions O2- (in oxides) or hydroxyl [OH] 1- (in hydroxides). Characteristic representatives: quartz, corundum, magnetite, hematite oxides; limonite, bauxite – hydroxides.

Table 2. Average abundance for the first ten chemical elements in the earth's crust, % by mass and their mineral productivity.

Table-3. Average composition of the Earth and the earth's crust, % by mass (according to A.A. Beus, 1972)

5. Sulfides. There are more than 200 types of sulfur and similar minerals, but their total content in the earth’s crust is not high, about 1%. From a chemical point of view, they are derivatives of hydrogen sulfide H2S. The origin of sulfides is mainly hydrothermal, as well as magmatic, rarely exogenous. Minerals of the sulfide class are formed, as a rule, at a depth below the limit of penetration of atmospheric oxygen into the earth's crust.

Once in the near-surface region, sulfides are destroyed; in addition, when they react with water and oxygen, they form sulfuric acid, which has an aggressive effect on rocks. Thus, sulfides are a harmful impurity in natural building materials. The most common iron sulfides are pyrite and chalcopyrite; other representatives
-galena, sphalerite, cinnabar.

6. Sulfates. Sulfates are salts of sulfuric acid. Many of them are soluble in water, since they are sediments of sea or lake salt water bodies. Some sulfates are products of the oxidation zone; Sulfates are also known as products of volcanic activity. Sulfates account for 0.5% of the mass of the earth's crust. There are anhydrous and aqueous sulfates, containing, in addition to the anionic complex 2- common to all, also additional anions (OH) 1-. Representatives: barite, anhydrite - anhydrous, gypsum, mirabilite - aqueous.

7.Halides. This class includes fluoride, chloride and very rare bromide and iodide compounds. Fluorine compounds, for the most part, are associated with magmatic activity; they are sublimations of volcanoes or products of hydrothermal processes, and sometimes have sedimentary origin. Chloride compounds of Na, K and Mg are predominantly chemical sediments of seas and lakes and the main minerals of salt deposits. Halides make up about 0.5% of the mass of the earth's crust. Typical representatives: fluorite (fluorspar), halite (rock salt), sylvite, carnallite.

8. Phosphates. Minerals in this class are salts of phosphoric acid; the crystal structure of these minerals is characterized by the presence of anionic complexes [PO4]3-. These are mainly rare minerals; The most widespread minerals of igneous origin are apatite and sedimentary biogenic phosphorites having the same chemical composition.

9. Tungstates and molybdates. This class contains a small number of mineral species; the composition of minerals corresponds to salts
33 tungstic and molybdic acids. The main representatives are wolframite and scheelite.

10. Native elements. About 40 chemical elements are known in nature in their native state, but most of them are very rare; In general, native elements make up about 0.1% of the mass of the earth's crust. Metals found in the native state are Au, Ag, Cu, Pt, Sn, Hg; semimetals – As, Sb, Bi and nonmetals – S, C (diamond and graphite).

The classification of minerals is based on their chemical composition:

Table 1 -

The sequence of actions when determining the hardness of minerals: the mineral is drawn on glass (t. 5). If a scratch remains on the glass, then the hardness of the mineral is equal to or greater than 5. Then standard minerals with a hardness greater than 5 are used. For example, if the mineral being tested leaves a scratch on a standard with a hardness of 6, and when scratched with quartz, a deep scratch is obtained, then its hardness is 6, 5.

Some minerals have special, unique properties. This is how carbonates react with hydrochloric acid (calcite “boils” in a piece, dolomite in powder, magnesite in hot acid).

Halides have a characteristic taste (halite - salty).

Minerals are characterized by varying resistance to weathering. Some minerals are physically destroyed, forming fragments, while other minerals undergo chemical transformations, transforming into other compounds (Table 2).

Resistance of minerals to weathering

table 2

Method for determining minerals.

To perform practical work, it is necessary to use a mineral determinant.

Sequence of work:

1. Determine the appearance of the grains of the mineral aggregate.

2. Determine the color of the mineral; if the mineral is dark in color, then run the mineral over a porcelain plate to determine the color of the streak (powder).

3. Determine the luster of the mineral.

4. To determine the hardness range, run the mineral across the glass.

5. Minerals of medium hardness (3-3.5) must be tested for reaction with a 10% solution of hydrochloric acid.

6. Try to find smooth polished edges on the sample - i.e. determine cleavage.

7. Using the set of characteristics in the determinant, find the name and composition of the mineral.

8. Note which rocks this mineral is included in.

Enter data on minerals in Table 3.

Characteristics of rock-forming minerals

Table 3

Exercise

List of minerals to study:

1. Native elements: graphite, sulfur.

2. Sulfides: pyrite.

3. Oxides and hydroxides: quartz, chalcedony, opal, limonite.

4. Halides: halite, sylvite.

5. Carbonates: calcite, dolomite, magnesite.

6. Sulfates: gypsum, anhydrite.

7. Silicates: olivine, garnet, augite, hornblende, talc, serpentine, kaolin, micas, chlorite, orthoclase, microcline, albite, nepheline.

BIBLIOGRAPHY

Pavlinov V.N. and others. A manual for laboratory classes in general geology. - M.: Nedra, 1988. p. 5-7, 11-49.

Study of igneous rocks

Purpose of the work: to acquire skills in identifying igneous rocks. Study the engineering and construction characteristics of igneous rocks and their use in construction.

Equipment: educational collection of igneous rocks, magnifying glasses, Mohs scale.

General information about rocks

Rocks are independent geological bodies consisting of one or more minerals of more or less constant composition and structure.

According to the method and conditions of formation, all rocks are divided into igneous, sedimentary and metamorphic.

The mineralogical composition of rocks is different. They can consist of one (monomineral) or several minerals (polymineral).

The internal structure of rocks is characterized by their structure and texture.

Structure is the structure of a rock, determined by the shape, size and relationships of its constituent parts.

The texture of a rock determines the distribution of its constituent parts in space.

All rocks are classified according to the conditions of formation into igneous, sedimentary and metamorphic rocks.

Conditions for the formation of igneous rocks

Igneous rocks form when magma cools. Magma is a rock melt of silicate composition that forms at great depths in the bowels of the Earth. Magma can cool deep in the Earth's crust under the cover of overlying rocks and at or near the surface of the Earth. In the first case, the cooling process proceeds slowly, and all the magma has time to crystallize. The structures of such deep rocks are holocrystalline and granular.

When magma quickly rises to the surface of the earth, its temperature drops quickly, gases and water vapor are separated from the magma. In this case, the rocks are either not completely crystallized (vitreous structure) or partially crystallized (semi-crystalline structure).

Deep rocks are called intrusive. Their structures can be: fine-grained (grains<0,5 мм), среднезернистая (размер зерен 0,5-1 мм), крупнозернистая (от 1 до 5 мм), гигантозернистая (>5 mm), unevenly grained (porphyritic).

Extruded rocks are called effusive. Their structures are porphyritic (individual large crystals stand out in the cryptocrystalline mass), aphanitic (dense cryptogranular mass), glassy (the rock consists almost entirely of non-crystallized mass - glass).

Igneous Rock Textures: Intrusive rocks are almost always massive. In effusive rocks, along with massive textures, there are porous and vesicular ones.

The physicochemical conditions for the formation of rocks at depth and on the surface are sharply different. For this reason, different rocks are formed from magma of the same composition in deep and surface conditions. Each intrusive rock corresponds to a specific extrusive rock.

Along with the classification of igneous rocks according to their occurrence conditions, they are classified according to their chemical composition depending on the content of silicic acid SiO 2 (Table 4).

Classification of igneous rocks

Table 4

Engineering and construction characteristics of igneous rocks.

All igneous rocks have high strength, significantly exceeding the loads possible in engineering and construction practice, are insoluble in water and practically waterproof (except for fractured varieties). Due to this, they are widely used as foundations for critical structures (dams). Complications during construction on igneous rocks arise if they are cracked and weathered: this leads to a decrease in density, an increase in water permeability, which significantly worsens their engineering and construction properties.

Application in construction

Intrusive igneous rocks such as granite, syenite, diorite, gabbro, labradorite are used as facing material.

Engineering-geological properties of metamorphic rocks

Massive metamorphic rocks have high strength, are practically waterproof and, with the exception of carbonate rocks, are insoluble in water.

The weakening of strength indicators occurs due to cracking and weathering.

Shale rocks are characterized by anisotropy of properties, i.e. the strength is significantly lower along the foliation than perpendicular to it. Such metamorphic rocks form thin-platy mobile screes.

The most durable and stable rocks are quartzites. Metamorphic rocks are widely used in construction. Marbles and quartzites are facing materials.

Roofing slates (phyllites) serve as a material for covering buildings.

Talc shale is a fire-resistant and acid-resistant material.

Quartzites are used as a raw material for the production of refractory bricks - dinas.

Methodology for determining metamorphic rocks

Determining metamorphic rocks must begin with establishing their mineral composition. Then the texture, structure, color and original rock are determined.

EXERCISE

Study the metamorphic rocks in the educational collection based on their external characteristics. Describe them in your notebook according to the following plan:

1. Title;

3. Structure and texture;

4. Mineral composition;

5. Source breed;

6. Engineering and geological features;

7. Application in construction.

BIBLIOGRAPHY

Pavlinov V.N. and others. A manual for laboratory classes in general geology. - M.: Nedra, 1988. p. 77-85.

Geological maps and sections

Purpose of the work: to master the principle of constructing geological maps and sections. Learn to read symbols of geological maps. Acquire skills in determining the conditions of occurrence of rocks using geological maps.

General information

A geological map reflects the geological structure of the earth's surface and the adjacent upper part of the earth's crust. A geological map is built on a topographic basis. Using symbols, it shows the age, composition and conditions of occurrence of rocks exposed on the earth’s surface.

Since more than 90% of the land surface is covered with Quaternary rocks, geological maps show bedrock without a Quaternary cover.

For construction purposes, large-scale geological maps (1:25000 and larger) are used.

When compiling geological maps, it is necessary to know the age (geochronological) sequence of rocks involved in the structure of the area being studied.

Currently, a unified geochronological scale has been created, reflecting the history of the development of the earth's crust.

The scale adopts the following temporary and corresponding stratigraphic (stratum - layer) divisions (Table 6).

Geochronological and stratigraphic divisions

Table 6

Geochronological scale

Table 7

Symbols on geographical maps

To indicate the composition, time of formation and conditions of occurrence of rocks on geological maps, color, letter, number and line symbols are used.

Color symbols are used to indicate the age of rocks, as well as the composition of intrusive and volcanic rocks (see geochronological scale). Letters and numbers (indices) indicate age, and for intrusive and volcanic rocks, their composition. For example (Figure 1):

Figure 1 - Designation of age of rocks

Stratigraphic terms are used to refer to rocks, for example: rocks of the Carboniferous system (not of the period).

To indicate the genesis of sedimentary rocks, lowercase Latin letters are used: m - marine, g - glacial, and - alluvial. For example: aQ - alluvial Quaternary deposits.

Intrusive and effusive rocks are indexed using capital Greek letters: γ - granites, δ - diorites, ξ - syenites, ν - gabbro, σ - dunites.

Line symbols are usually used on geological maps made in one color, as well as on sections and stratigraphic columns

The most commonly used line symbols are shown in Figure 2.

1 - sands; 2 - sandstones; 3 - pebbles; 4 - conglomerates; 5 - siliceous rocks (jasper, opoka, diatomite); 6 - limestones; 7 - dolomites; 8 - clay; 9 - marls; 10 - rocks of acidic composition; 11 - their lavas and tuffs; 12 - rocks of average composition; 13 - their lavas and tuffs; 14 - basic rocks; 15 - their lavas and tuffs.

Figure 2 - Line symbols

Layer and layering

A layer (or stratum) is a more or less homogeneous isolated sediment (or rock) bounded by bedding surfaces.

The upper surface is called the roof, the lower - the sole. The distance between the roof and the sole characterizes its power.

There are two possible cases of the relationship between layered strata. In the first, each overlying strata, without traces of a break in the accumulation of sediments, lies on the underlying layers, forming a conformable occurrence of rocks.

In the second case, the stratigraphic sequence is interrupted between the strata and, as a result, a stratigraphic e disagreement, which can also be angular (Figure 3).

Figure 3 - Unconformity of rocks

Stratigraphic columns and geological sections

Geological maps are usually accompanied by stratigraphic columns and sections. On the stratigraphic column in age sequence from bottom to top from ancient to young, conventional shading depicts pre-Quaternary sedimentary, volcanic and metamorphic rocks developed in the territory. Intrusive formations are not shown on the column.

Geological sections are an image of the occurrence of rocks on a plane of vertical section of the earth's crust from its surface to a particular depth.

The horizontal and vertical scales of the sections must correspond to the map scale (except for cases where the rock occurrence is horizontal). Each section shows: a hypsometric profile of the terrain, a sea level line, a vertical scale with divisions of 1 cm at both ends of the section.

Sections are colored and indexed in accordance with the geological map.

When layers occur horizontally, sections are usually built through the highest and lowest points of the relief.

During construction, it is important to know the geological structure of the upper part of the earth's crust. The upper horizons are mainly characterized by the horizontal occurrence of rocks.

Guidelines and tasks for constructing a geological section

The appendix (issued by the teacher) contains a geological map of the river basin. Kacha and stratigraphic column. It is necessary to study the sequence of occurrence of rocks in the column, their description, age, thickness. Glue a photocopy of the map onto a sheet of Whatman paper size A4, and draw a stratigraphic column to the left of the map. Place symbols on the right. The geological section is made below (Figure 4).

Geological map of the river basin Kacha

Scale 1:25000

Geological section according to AB

The scale of the mountains.

Figure 4 - Location of drawing elements

The construction of the section begins with drawing the profile of the section. To do this, several horizontal lines are drawn on a sheet of whatman paper, the distance between which should be equal to the section of the relief with horizontal lines on the scale of the map. In a given map, contour lines cut the relief every 10 m, which on a scale of 1:10000 will be 1 mm. Rulers are limited by vertical lines located at a distance corresponding to the length of the cut. The vertical rulers on both sides of the section indicate the heights corresponding to the height of the contour lines on the map intersected by the section line. Next, measure on the map the distances to the cut line up to the intersection with the horizontal lines and transfer these distances to rulers having the same elevation marks. The resulting points are connected by a smooth curve, which will represent the relief profile.

Having drawn a relief curve of the Earth's surface along the cut line, transfer to it all the points of intersection of the cut line with geological boundaries. For this purpose, you can use either a measuring compass or a separate narrow strip of paper. Having found the exit points of geological boundaries on the relief surface, we draw horizontal lines between the stratigraphic complexes. The letters A and B are placed at the ends of the section, and indices and conventional shading for the rocks are applied to the section itself.

Exercise

Construct a geological section along the line proposed by the teacher, using the educational map in the application (issued by the teacher).

Bibliography

Pavlinov V.N. and others. A manual for laboratory classes in general geology. - M.: Nedra, 1988. P. 86-102.

Assessment of engineering and geological conditions of construction

Purpose of the work: to acquire skills in processing primary data from engineering geological surveys and their evaluation. Equipment: sheet of whatman paper 70x30 cm, drawing supplies.

Modern construction methods make it possible to develop even areas with very difficult natural conditions, but this requires large additional capital investments. Assessing the feasibility of such costs and the suitability of a particular territory for construction is always associated with establishing the volume of engineering measures necessary for the development of the site.

For this purpose, engineering and geological surveys are carried out, the analysis of which allows:

1. Assess the engineering-geological conditions of construction of structures, assess the possible impact of structures on the condition and properties of rocks and the stability of the territory as a whole;

2. Establish the nature of engineering measures that ensure the stability and reliability of structures.

By completing this final work, the student gains some skills in processing primary geotechnical survey data and evaluating them.

Exploratory drilling and leveling data are used as source materials.

The work consists of two stages:

1) construction of a geological section based on well drilling data;

2) drawing up an explanatory note for the constructed section.

Methodology for constructing a geological section.

The student completes the version of the task whose number matches the last digit of his code. Based on leveling and drilling data, construct a geological section on the scale: horizontal 1: 5000, vertical

1: 500. Drilling data in the application (issued by the teacher).

To construct a section, you need a sheet of whatman paper 70 x 30 cm. The drawing is done in pencil.

On the left side of the sheet we draw a vertical scale bar in the accepted scale (1: 500). The maximum elevation on this ruler is equal to the maximum absolute elevation of the terrain (according to leveling data), the minimum is equal to the lowest absolute elevation of the well bottom (well penetration depth). Under the scale ruler we draw a conditional base line equal to the length of the section. Next, we plot on the base line on a horizontal scale (1: 5000) the distance between the points in accordance with the leveling data. From the points we restore perpendiculars to the absolute elevations of the earth's surface (wellheads).

By connecting the wellheads with a smooth line, we obtain a topographic profile line (ground surface). Next to the wellhead we indicate the number and absolute elevation of the wellhead. On the axial lines of the wells, with small horizontal strokes we show the boundaries of the distribution of thickness in m of certain rocks from top to bottom, and next to them we indicate with symbols the lithological composition and age of the rocks, that is, we plot the sections of these drill holes.

Next, we connect the strokes depicting the boundaries of rocks of the same composition and age in neighboring wells. If the rock found in one well is absent in the next one, then on the section we depict it as gradually wedging out towards the middle of the distance between the wells. After linking all rock boundaries, we shade the areas between the wells according to the symbols (Figure 2).

We mark the mark for the appearance of the groundwater level next to the excavation on the right at a height corresponding to this mark.

We connect the position of the groundwater level into a single dotted line, and show the established levels of pressure water next to the mine with a vertical arrow to the height of the water pressure (from the mark of appearance to the mark of establishment of pressure water).

We place symbols of rocks in strict sequence from younger to older and apply them to the right of the section (from top to bottom) or under the section (from left to right). We sign the incision below. For example: “Geological-lithological section along the line of wells (1-5).” Under the name in the middle we place the horizontal and vertical scale.

An explanatory note must be attached to the geological and lithological profile, including a description of:

1) terrain;

2) geological structure;

3) hydrogeological conditions;

4) engineering and geological conditions of construction.

Terrain.

It is necessary to indicate the type of relief (mountainous or flat), the degree of its ruggedness and the absolute marks of individual elements. Particular attention is paid to the description of the river valley: length, width, depth of the river bed, the presence of terraces, their heights above the water level, width, steepness of the bedrock slopes.

Based on their location relative to the riverbed, symmetrical and asymmetrical terraces are distinguished, as well as two-sided and one-sided floodplains. According to the conditions of formation, terraces are divided into accumulative (composed entirely of alluvium), erosional (composed entirely of bedrock) and basement (in which part of the slope above the river is represented by bedrock, covered with a layer of alluvium on top).

Geological structure.

Here the lithological and stratigraphic characteristics of the rocks and the conditions of their occurrence are given.

First, the age of bedrock and the conditions of their occurrence, as well as the genetic varieties of Quaternary deposits are given.

Eluvium (e) - clastic material is formed under the influence of weathering and forms an accumulation at the site of destruction.

Colluvium (d) - detrital material carried along a slope by rain or melt water and accumulates on a slope or at the foot of hills.

Proluvium (p) - destruction products carried by powerful temporary flows (mudflows) to the foot of the hills and located in the form of alluvial cones.

Alluvium (a) - deposits formed in river valleys by river flows.

Colluvium (q) - clastic sediments transported downslope by gravity.

Fluvioglacial (fq) - deposits of glacial meltwater flows below the edge of the glacier.

Then they begin a detailed description of the breed according to plan:

a) name of the breed, group by genesis, age;

b) mineralogical composition, structure, texture;

c) power and its change along the profile;

d) conditions of occurrence.

The description of the rocks is carried out in age sequence from ancient to young.

Hydrogeological conditions.

When characterizing hydrogeological conditions, the presence of various types of groundwater and the total number of aquifers are noted. For each aquifer, the following information is provided: type of groundwater (upper water, groundwater, interstratal, fractured), confined or non-confined.

It is necessary to pay attention to the hydraulic connection between neighboring aquifers (the connection is established by the coincidence of piezometric levels between pressure horizons, or with the horizon of overlying groundwater).

Engineering and geological conditions of construction.

An assessment of the engineering-geological conditions of construction is given in the form of an analysis of the engineering-geological properties of rocks (density, humidity, water permeability, resistance to mechanical stress, subsidence, swelling, sliding, karst formation and other geological phenomena).

Requirements for the composition and design of the work.

The volume of the explanatory note is 5-6 pages of handwritten text on A4 sheets. The title page is carried out according to generally accepted requirements for written work, indicating the version number.

To complete the work you will need literature.

The text should be concise and at the same time detailed and comprehensive.

At the end of the work there is a list of references used.

BIBLIOGRAPHY

Ananyev V.P. Engineering Geology. - M.: Higher School, 2000.

Currently, more than 3,000 minerals are known. The modern classification of minerals is based on principles that take into account the most essential characteristics of mineral species - chemical composition and crystal structure.

In this classification, the basic unit is taken to be a mineral species that has a certain crystalline structure and a certain stable chemical composition. The mineral type can have varieties. A variety is understood as minerals of the same type that differ from each other in some physical attribute, for example, in the color of the mineral quartz in numerous varieties (black - morion, transparent - rock crystal, purple - amethyst).

In accordance with this, the classification can be presented as follows:

1. Native

2. Sulfides

3. Halides

4. Oxides and hydroxides

5. Carbonates

6. Sulfates

7. Phosphates

8. Silicates

1. Native elements (minerals).

This class includes minerals consisting of one chemical element and named after this element. For example: native gold, sulfur, etc. All of them are divided into two groups: metals and non-metals. The first group includes native Au, Ag, Cu, Pt, Fe and some others, the second - As, Bi, S and C (diamond and graphite).

Genesis (origin) - mainly formed during endogenous processes in intrusive rocks and quartz veins, S (sulfur) - during volcanism. During exogenous processes, rocks are destroyed, native minerals are released (due to their resistance to physical and chemical influences) and their concentration in places favorable for this. Thus, placers of gold, platinum and diamond can be formed.

Application in the national economy:

1- jewelry production and foreign exchange reserves (Au, Pt, Ag, diamonds);

2- cult objects and utensils (Au, Ag),

3- radio electronics (Au, Ag, Cu), nuclear, chemical industry, medicine, cutting tools - diamond;

4- agriculture - sulfur.

2. Sulfides– salts of hydrosulfide acid.

Divided into simple with the general formula A m X p and sulfosalts– A m B n X p, where – A is a metal atom, B is atoms of metals and metalloids, X is sulfur atoms.

Sulfides crystallize in different systems - cubic, hexagonal, orthorhombic, etc. Compared to native ones, they have a wider composition of element cations. Hence there is a greater variety of mineral species and a wider range of the same property.

Common properties for sulfides are metallic luster, low hardness (up to 4), gray and dark colors, and medium density.

At the same time, among sulfides there are differences in such properties as cleavage, hardness, and density.

Sulfides are the main source of non-ferrous metal ores, and due to the admixtures of rare and noble metals, the value of their use increases.

Genesis - various endogenous and exogenous processes.

3.Halides. The most widespread are fluorides and chlorides, compounds of metal cations with monovalent fluorine and chlorine.

Fluorides are light-colored minerals of medium density and hardness. Representative is fluorite CaF2. The chlorides are the minerals halite and selvite (NaCl and KCl).

The common features of halogens are low hardness, crystallization in the cubic system, perfect cleavage, a wide range of colors, and transparency. Halite and sylvite have special properties - salty and bitter-salty taste.

Fluorides and chlorides differ in their genesis. Fluorite is a product of endogenous processes (hydrothermal), and halite and sylvite are formed under exogenous conditions due to precipitation during evaporation in water bodies.

In the national economy, fluorite is used in optics, metallurgy, and for the production of hydrofluoric acid. Halite and sylvite are used in the chemical and food industries, medicine and agriculture, and photography.

4. Oxides and hydroxides– represent one of the most common classes with more than 150 mineral species in which metal atoms or cations form compounds with oxygen or a hydroxyl group (OH). This is expressed by the general formula AX or ABX - where X is the oxygen atoms or hydroxyl group. The most widely represented oxides are Si, Fe, Al, Ti, and Sn. Some of them also form the hydroxide form. A feature of most hydroxides is a decrease in property values ​​compared to the oxide form of the same metal atom. A striking example is the oxide and hydroxide forms of Al.

Oxides can be divided into metallic and nonmetallic based on their chemical composition and luster. The first group is characterized by medium hardness, dark colors (black, gray, brown), and medium density. An example is the minerals hematite and cassiterite. The second group is characterized by low density, high hardness 7-9, transparency, a wide range of colors, and lack of cleavage. Example p - minerals quartz, corundum.

In the national economy, oxides and hydroxides are most widely used to produce Fe, Mn, Al, Sn. Transparent, crystalline varieties of corundum (sapphire and ruby) and quartz (amethyst, rock crystal, etc.) are used as precious and semi-precious stones.

Genesis – during endogenous and exogenous processes.

5. Carbonates– salts of carbonic acid, general formula ACO3 – where A is Ca, Mg, Fe, etc.

General properties - crystallizes in rhombic and trigonal systems (good crystalline forms and rhombic cleavage); low hardness 3-4, predominantly light color, reaction with acids (HCl and HNO3) with the release of carbon dioxide.

The most common are: calcite CaCO3, magnesite Mg CO3, dolomite CaMg (CO3)2, siderite Fe CO3.

Carbonates with a hydroxyl group (OH): Malachite Cu2 CO3 (OH)2 – green color and reaction with HCl, Lapis lazuli Cu3 (CO3)2 (OH)2 – blue color, transparent in crystals.

The genesis of carbonates is diverse - sedimentary (chemical and biogenic), hydrothermal, metamorphic.

Carbonates are one of the main rock-forming minerals of sedimentary rocks (limestones, dolomites, etc.) and metamorphic ones - marble, skarns. They are used in construction, optics, metallurgy, and as fertilizers. Malachite is used as an ornamental stone. Large accumulations of magnesite and siderite are a source of iron and magnesium.

6. Sulfates– salts of sulfuric acid, i.e. have SO4 radical. The most common and well-known sulfates are Ca, Ba, Sr, Pb. Their common properties are crystallization in monoclinic and orthorhombic systems, light color, low hardness, glassy luster, and perfect cleavage.

Minerals: gypsum CaSO4 2H2O, anhydrite CaSO4, barite BaSO4 (high density), celestine SrSO4.

They are formed under exogenous conditions, often together with halogens. Some sulfates (barite, celestine) are of hydrothermal origin.

Application – construction, agriculture, medicine, chemical industry.

7. Phosphates– salts of phosphoric acid, i.e. containing PO4.

The number of mineral species is small; we will consider the mineral apatite Ca(PO4)3(F,Cl,OH). It forms crystalline and granular aggregates, hardness 5, hexagonal system, imperfect cleavage, green-blue color. Contains impurities of strontium, yttrium, rare earth elements.

Genesis is magmatic and sedimentary, where it forms phosphorite when mixed with clay particles.

Application - agricultural raw materials, chemical production and in ceramic products.

8. Silicates- the most common and diverse class of minerals (up to 800 species). The taxonomy of silicates is based on the silicon-oxygen tetrahedron -4. Depending on the structure they form when connecting with each other, all silicates are divided into: island, layer, ribbon, chain and framework.

Island silicates - in them the connection between isolated tetrahedra is carried out through cations. This group includes minerals: olivine, topaz, garnets, beryl, tourmaline.

Layer silicates represent continuous layers, where tetrahedra are connected by oxygen ions, and between the layers the connection is carried out through cations. Therefore, they have a common radical in formula 4-. This group includes mica minerals: biotite, talc, muscovite, serpentine.

Chain and ribbon - tetrahedra form single or double chains (ribbons). Chain - have a common radical 4- and include a group of pyroxenes.

Ribbon silicates with radical 6- combine minerals of the amphibole group.

Framework silicates - in them, tetrahedra are connected to each other by all oxygen atoms, forming a framework with a radical. This group includes feldspars and plagioclases. Feldspars combine minerals with Na and K cations. These are microcline and orthoclase minerals. Plagioclases contain Ca and Na as cations, and the ratio between these elements is not constant. Therefore, plagioclases represent an isomorphic series of minerals: albite - oligoclase - andesine - labradorite - bytownite - anorthite. From albite to anorthite the Ca content increases.

The composition of cations in silicates most often contains: Mg, Fe, Mn, Al, Ti, Ca, K, Na, Be, less often Zr, Cr, B, Zn, rare and radioactive elements. It should be noted that part of the silicon in tetrahedra can be replaced by Al, and then we classify the minerals as aluminosilicates.

The complex chemical composition and diversity of the crystal structure combine to produce a wide range of physical properties. Even using the Mohs scale as an example, it can be seen that the hardness of silicates ranges from 1 to 9.

Cleavage varies from very perfect to imperfect.

Silicates are often grouped by color - dark-colored, light-colored. This is especially widely applied to silicates - rock-forming minerals.

Silicates are formed mainly during the formation of igneous and metamorphic rocks in endogenous processes. A large group of clay minerals (kaolin, etc.) is formed under exogenous conditions during the weathering of silicate rocks.

Many silicates are minerals and are used in the national economy. These are building materials, facing, ornamental and precious stones (topaz, garnets, emerald, tourmaline, etc.), metal ores (Be, Zr, Al) and non-metals (B), rare elements. They find application in the rubber and paper industries, as refractories and ceramic raw materials.

Along with the crystal chemical classification, there are other classifications of minerals based on other principles. For example, genetic classification is based on the type of genesis of minerals; in ore processing technology, classifications are used based on their physical (separation) properties, for example, magnetism, density, solubility, fusibility, and other characteristics.