Basic properties of minerals. Composition of wood-polymer composites: general properties of mineral fillers

When we examine minerals in museum showcases or trays with specially selected samples, we are involuntarily struck by the variety of external features by which they differ from each other.

Some minerals appear transparent (rock crystal, rock salt), others appear cloudy, translucent or completely opaque (magnetite, graphite).

A remarkable feature of many natural compounds is their color. For a number of minerals, it is constant and very characteristic. For example: cinnabar (mercury sulphide) always has a carmine-red color; malachite is characterized by a bright green color; cubic crystals of pyrite are easily recognized by their metallic golden color, etc. Along with this, the color of a large number of minerals is variable. Such, for example, are varieties of quartz: colorless (transparent), milky white, yellowish brown, almost black, purple, pink.

Shine is also a very characteristic feature of many minerals. In some cases, it is very similar to the brilliance of metals (galena, pyrite, arsenopyrite), in others - to the brilliance of glass (quartz), mother-of-pearl (muscovite). There are also quite a few minerals that even in a fresh fracture look matte, that is, they do not have a shine.

Often minerals are found in crystals, sometimes very large, sometimes extremely small, which can be seen only with a magnifying glass or microscope. For a number of minerals, crystalline forms are very typical, for example: for pyrite - cubic crystals; for garnets - rhombic dodecahedrons; for beryl - hexagonal prisms. However, in most cases, mineral masses are observed in the form of continuous granular aggregates, in which individual grains do not have crystallographic outlines. Many mineral substances are also distributed in the form of sinter masses, sometimes of a bizarre shape that has nothing to do with crystals. Such, for example, are kidney-shaped masses of malachite, stalactite-like formations of limonite (iron hydroxides).

Minerals also differ in other physical properties. Some of them are so hard that they easily leave scratches on glass (quartz, garnet, pyrite); others themselves are scratched by fragments of glass or a knife edge (calcite, malachite); others have such a low hardness that they are easily drawn with a fingernail (gypsum, graphite). Some minerals, when split, easily split along certain planes, forming fragments of the correct shape, similar to crystals (rock salt, galena, calcite); others give curved, "conchoidal" surfaces in fracture (quartz). Such properties as specific gravity, fusibility, etc., also vary widely.

The chemical properties of minerals are just as different. Some are easily soluble in water (rock salt), others are soluble only in acids (calcite), others are resistant even to strong acids (quartz). Most minerals are well preserved in the air. However, a number of natural compounds are known that are easily oxidized or decomposed due to oxygen, carbon dioxide and moisture contained in the air. It has also long been established that some minerals gradually change their color under the influence of light.

All these properties of minerals are causally dependent on the characteristics of the chemical composition of minerals, on the crystal structure of the substance and on the structure of the atoms or ions that make up the compounds. Much that previously seemed mysterious, now, in the light of modern achievements in the exact sciences, especially physics and chemistry, is becoming more and more clear.

In this regard, let us recall some of the most important for us provisions of physics, chemistry, crystal chemistry and colloid chemistry.

Aggregate states of minerals. As already mentioned, according to the existing three states of aggregation of matter, minerals are distinguished solid, liquid and gaseous.

Any substance of inorganic nature, depending on temperature and pressure, can be in any state of aggregation, and when these factors change, it passes from one state to another.

The stability limits of each state of aggregation are in very different temperature ranges, depending on the nature of the substance. At atmospheric pressure at room temperature, most minerals are in a solid state and melt at high temperatures, while mercury under these conditions exists in liquid form, and hydrogen sulfide and carbon dioxide exist in a gaseous state.

Most solid minerals are represented crystalline substances, i.e., substances with a crystalline structure. Each crystalline substance has a certain melting temperature, at which the change in the state of aggregation of the substance occurs with the absorption of heat, which clearly affects the behavior of the heating curves (Fig. 5, A). At a certain time interval, the heat influx reported to the system is spent on the melting process (the curve flattens out).

Crystallization of a cooled homogeneous liquid substance must occur at the same temperature as melting solid body of the same composition, but usually it occurs with some cooling liquids, which must always be kept in mind.

Solid chemically pure substances characterized by a disordered structure, i.e., the absence of a regular arrangement of atoms, are called amorphous(glassy) bodies. They belong to the number of isotropic substances, i.e., having the same physical properties in all directions. A characteristic feature of amorphous substances, in contrast to crystalline ones, is also gradual transition one state of aggregation to another along a smooth curve (Fig. 5, B) like sealing wax, which, when heated, gradually becomes flexible, then viscous, and, finally, drop-liquid.

Amorphous substances are often obtained during the solidification of molten viscous masses, especially when the melt is cooled very quickly. An example is the formation of the mineral leschatellerite - amorphous quartz glass during a lightning strike into quartz crystalline rocks. The transition of amorphous substances into crystalline masses can occur only when they are kept in a softened state for a long time at a temperature close to the melting point.

It should be added that not all substances can be easily obtained in the amorphous state. Such, for example, are metals which, even when quenched, do not form glassy substances.

Polymorphism. Polymorphism ("poly" in Greek - many) is the ability of a given crystalline substance, when external factors (mainly temperature) change, to undergo two or more modifications of the crystal structure, and in connection with this, changes in physical properties. The most striking example in this regard is the dimorphism of natural carbon, which crystallizes, depending on the conditions, either in the form of diamond (cubic system) or graphite (hexagonal system), which differ greatly from each other in physical properties, despite the identity of the composition. When heated without access to oxygen, the crystal structure of diamond at a temperature above 3000 ° at atmospheric pressure is rearranged into a graphite structure that is more stable (stable) under these conditions. The reverse transition of graphite to diamond is not established.

Figure 6. Changes in the properties of quartz when heated. I - rotation of the plane of polarization; II - the value of the birefringence; III - refractive index Nm (for the D line of the spectrum)

Sometimes a polymorphic transformation is accompanied by a very slight change in the crystal structure of the substance, and therefore, without subtle studies, it is not possible to notice any significant changes in the physical properties of the mineral. Such, for example, are the transformations of the so-called α-quartz into β-quartz and vice versa. However, a study of the optical properties (Fig. 6) unambiguously shows an abrupt change at the transition point (about 573°) of such properties as refractive indices, birefringence, and rotation of the optical polarization plane.

Differences of a given crystalline substance that are stable under certain specific physicochemical conditions are called modifications, each of which is characterized by a specific crystal structure characteristic of it. A given substance may have two, three or more such polymorphic modifications (for example, six modifications have been established for sulfur, of which only three occur in nature, for SiO 2 - nine modifications, etc.).

Various polymorphic modifications are usually indicated by Greek letters α, β, γ, etc. prefixes to the name of the mineral (for example: α-quartz, stable below 573°; β-quartz, stable above 573°, etc.). There is no uniformity in the order of naming the modifications in the literature: some adhere to the designation of various modifications with the letters α, β ... in the order of increasing or decreasing the transformation temperature, others use the order of designations according to the degree of prevalence or in the order of discovery. The first order of designation should be considered more rational.

The phenomena of polymorphism are very widespread among natural compounds. Unfortunately, they are still far from sufficiently studied. Polymorphic modifications of various minerals can be stable in the most diverse ranges of changes in external factors (temperature, pressure, etc.). Some have a wide field of stability with very significant fluctuations in temperature and pressure (diamond, graphite), while others, on the contrary, undergo polymorphic transformations within a narrow range of changes in external factors (sulfur).

The very fact of rearrangement of the crystal structure with a change in external equilibrium factors, as V. M. Goldshmidt believes, is due not to the fact that interatomic or interionic distances change, but to the fact that there are strong changes in the mutual polarization of structural units held in the lattice by electrostatic forces . In the simplest case, at the moment of the critical state, the coordination number changes, indicating a fundamental change in the structure of the substance.

It often happens that the high-temperature modification of a mineral, when converted into a lower-temperature modification, retains the external shape of the original crystals. Such cases of false forms are called paramorphosis. An example is the paramorphosis of calcite after aragonite (CaCO3).

If a given modification of a crystalline substance, let's say α, has the property of changing external conditions (for example, temperature) to go into another - β-modification, and when the previous conditions are restored, it turns back into an α-modification, then such polymorphic transformations are called enantiotropic*. Example: conversion of orthorhombic α-sulfur to monoclinic β-sulfur and vice versa. If the reverse transition cannot occur, then this type of transformation is called monotropic. An example is the monotropic transformation of rhombic aragonite (CaCO 3) into trigonal calcite (when heated).

* ("Enantios" in Greek - opposite, "tropos" - change, transformation)

In nature, the simultaneous existence of two modifications under the same physical and chemical conditions is often observed, even next to each other (for example: pyrite and marcasite, calcite and aragonite, etc.). Obviously, the transition of one of the modifications to a stable, i.e. stable, was delayed for some reason, and the substance in this case is in metastable(or, as they are otherwise called, labile, unstable) state, just as there are supercooled liquids.

It should be emphasized that the stable modification, in comparison with the unstable one, has:

1. lower vapor pressure
2. lower solubility and
3. higher melting point.

Phenomena of the destruction of crystal lattices. The main features spatial lattices of crystalline bodies are a regular arrangement and a strictly balanced state of their constituent structural units. However, it is enough to create conditions under which the internal bonds of structural units will be shaken, as from a crystalline substance with an ordered spatial lattice, we will get an amorphous mass that does not have a crystalline structure.

An excellent example in this regard is the mineral ferrobrucite - (Mg,Fe) 2 containing up to 36% (by weight) of ferrous oxide as an isomorphic impurity. In its fresh state, this mineral, when extracted from the deep horizons of mines, is completely colorless, transparent and has a glassy luster. Over the course of several days, its crystals gradually change color when exposed to air, becoming golden yellow, then brown, and finally opaque dark brown, retaining their external crystalline form*. Chemical analysis shows that almost all of the ferrous iron is transformed into trivalent iron (i.e., oxidation occurs), and X-ray examination does not establish signs of a crystalline structure. Obviously, the oxidation of iron broke the internal bonds in the crystal lattice, which led to the disorganization of the structure of the substance.

* (Brucite, which does not contain iron, is quite stable under similar conditions.)

What happens to ferrobrucite in an oxidizing environment at room temperature and atmospheric pressure can take place for other minerals at elevated temperatures and pressures, as has already been established for a number of cases.

Very interesting phenomena have been studied in minerals containing rare-earth and radioactive elements (orthite, fergusonite, aeschinite, etc.). They also very often, but not always, establish the transformation of a crystalline substance into an amorphous one, which is supposed to be due to the action of α-rays during radioactive decay *. These altered glassy minerals, which do not belong to the cubic system, are optically isotropic and do not show X-ray diffraction, i.e., they behave like amorphous bodies. In this case, partial hydration of the substance occurs. Brögger called such bodies metamict.

* (According to V. M. Goldshmidt, to achieve an amorphous state in these cases, the radioactivity of the mineral alone is not enough, but the following two conditions are also necessary:

1. the initially emerging crystalline substance must have a weak ionic lattice, allowing rearrangement or hydrolysis; such lattices are formed mainly when weak bases are combined with weak anhydrides;
2. the lattice must contain one or more types of ions that can easily be recharged (for example, rare earth ions) or even turn into neutral atoms (for example, the formation of atomic fluorine in fluorite under the influence of radioactive radiation from outside)

The process of decay itself is presented by V. M. Goldshmidt as a rearrangement of matter. For example, the YNbO 4 compound is converted into a fine mixture (solid pseudo-solution) of oxides: Y 2 O 3 and Nb 2 O 5 . With this concept, it is understandable why no transformations into an amorphous substance of simple compounds, such as ThO 2 (thorianite), or salts of strong acids with weak grounds, e.g. (Ge, La...) PO 4 (monazite))

In confirmation of the phenomena of decomposition of crystalline media, a number of other similar examples can be cited, illustrating the formation of amorphous or colloidal masses. However, one cannot think that these new formations are a stable form of the existence of matter. There are many known examples of the secondary rearrangement of matter with the formation of new crystalline bodies that are stable under changed conditions. Thus, "ilmenite crystals" (Fe .. TiO 3) are known, which, upon microscopic examination, turn out to be composed of a mixture of two minerals: hematite (Fe 2 O 3) and rutile (TiO 2). Apparently, after the moment of formation of ilmenite in some period of the life of the mineral, under the influence of a changed oxygen regime, sharply oxidizing conditions were created, which led to the transition of Fe 2+ to Fe 3+ with the simultaneous decomposition of the crystal structure, and then to a gradual rearrangement of the substance with the formation of a mixture sustainable minerals. In the same way, for example, there were cases of formation of tillite (PbSnS 2), galena (PbS) and cassiterite (SnO 2) in place in the closest intergrowth with each other, but while maintaining the relict (i.e., the former) lamellar-granular structure of the aggregate characteristic of tillite. Obviously, due to the increased at some point in the concentration of oxygen in this environment, tin, having a high affinity for oxygen, separated from the initially homogeneous mineral mass in the form of an oxide, and lead passed into the form of an independent sulfur compound.

The concept of colloids*. In addition to clearly crystalline formations, the crystalline nature of which is easily established by eye or under a microscope, colloids are also widely used in the earth's crust.

* ("Kolla" in Greek - glue, "colloid" - glue-like)

Colloids are called heterogeneous (heterogeneous) dispersed * systems, consisting of "dispersed phase" and "dispersion medium".

* (Dispersion - scattering; in this case, the state of matter in the form of the smallest particles. The degree of dispersion is determined by the size of these particles)

The dispersed phase in these systems is represented by finely dispersed particles (micelles) of any substance in any mass (dispersion medium). The particle sizes of the dispersed phase range from approximately 100 to 1 mμ (from 10 -4 to 10 -6 mm), i.e., much larger than the sizes of ions and molecules, but at the same time so small that with the help of a conventional microscope are indistinguishable. Each such particle may contain from several to many tens and hundreds of molecules of a given compound; in solid particles, ions or molecules are bound into a crystal lattice, i.e., these particles are the smallest crystalline phases.

The state of aggregation of the dispersed phase and the dispersion medium can be different (solid, liquid, gaseous), and their most diverse combinations can be observed. Denoting the state of aggregation of the dispersion medium in capital letters, and the state of the dispersed phase in small letters, we give the following examples:

• G+t: tobacco smoke; soot
• G+F: Fog
• W+t: yellow peaty waters; healing mud
• F + g: hydrogen sulfide sources; foam
• W+W: Typical emulsions (e.g. milk)
• T + w: crystals of native sulfur with liquid bitumen sprayed into them; opal
• T+t: red calcite with iron oxide finely dispersed in it
• T + g: milky white minerals containing gases

Among the colloidal formations, there are sols and gels.

Typical sols, otherwise called colloidal solutions or pseudo-solutions, are such formations in which the dispersion medium strongly predominates over the dispersed phase (for example: tobacco smoke, yellow-brown ferruginous waters, milk). To the eye, such solutions appear completely homogeneous and often transparent, indistinguishable from true (ionic or molecular) solutions. In sols in which the dispersion medium ("solvent") is represented by water, particles of the dispersed phase easily pass through ordinary filters, but do not penetrate through animal membranes. If their size exceeds 5 mμ, then they can be easily detected in an ultramicroscope using the so-called Tyndall light cone, which is created by side illumination of a special glass vessel filled with a colloidal solution. The effect created in this case is completely analogous to what we usually observe in a darkened room in a beam of light emanating from a projection lamp: particles of the dispersed phase become visible in the luminous cone, performing Brownian motion, which is never observed in true solutions, with the exception of solutions of some organic compounds with very large molecules.

V gels the dispersed phase is presented in such a significant amount that the individual dispersed particles are, as it were, stuck together, forming gelatinous, glue-like, glassy masses. The dispersion medium in these cases, as it were, occupies the remaining space between the dispersed particles. Examples of gels can be: soot, dirt, opal (silica gel), limonite (iron hydroxide gel), etc.

Depending on the nature of the dispersion medium, there are: hydrosols and hydrogels (dispersion medium - water), aerosols and aerogels (dispersion medium - air), pyrosols and pyrogels (dispersion medium - any melt), crystal sols and crystal gels (dispersion medium - some or a crystalline substance), etc.

Hydrosols, crystalsols and hydrogels are the most widespread in the earth's crust. In what follows, we will only talk about them.

hydrosols most easily obtained mechanically, by fine atomization in one way or another of the substance to the size of the dispersed phase in water. In nature, coarse and finely dispersed systems are often formed during grinding and abrasion of rocks and minerals under the influence of driving forces (water flows, glaciers, tectonic displacements, etc.).

However, the greatest role in the formation of natural colloidal solutions is played by chemical reactions in aqueous media leading to the condensation of molecules: oxidation, reduction and, especially, reactions of exchange decomposition. For the most superficial earth's crust no less important in the formation of colloids is also the vital activity of organisms (biochemical processes).

It is important to note that dispersed particles in colloidal solutions are electrically charged, which can be easily seen when passing through solutions electric current. The sign of the charge is the same for all particles of a given colloid, due to which, repelling each other, they are in a suspended state in a dispersion medium. The appearance of a charge is explained by the adsorption of certain ions contained in solutions by dispersed particles. This issue needs to be considered in more detail.

Imagine, for example, a solid dispersed AgBr particle. Despite its ultramicroscopic dimensions, it should have a crystalline structure, which is shown schematically in section in Fig. 7. Each of the Ag 1+ cations and Br 1- anions inside this lattice is in a six-wheel environment of ions of opposite charge: four in the plane of the drawing, one above the given ion and one below it. Thus, the internal ions of a dispersed particle are completely saturated with valences. The situation is different with boundary ions in the crystal lattice. In the same way, it is easy to calculate that most of the outer ions on the face perpendicular to the plane of the pattern receive saturation only from five ions of the opposite sign (three in the plane of the pattern, one above and one below the plane of the pattern). Consequently, the Ag and Br ions located on the flat surface of a dispersed particle have 1/6 of the unsaturated valence each, and 2/6 each on the edges, and corner ions even have 3/6 of the unsaturated valence each. It is this residual uncompensated charge that causes the absorption (adsorption) of a certain amount of additional bromine or silver ions from the solution, which are held at the surface of dispersed particles in the form of a so-called diffuse layer.

In practice, AgBr colloid is obtained by mixing solutions of AgNO 3 and KBr, reacting according to the following scheme: AgNO 3 + KBr = AgBr + KNO 3. If these solutions are mixed in equivalent amounts, then a crystalline precipitate of AgBr is formed (but not a colloid). If silver nitrate is poured into potassium bromide, then a sol appears, the dispersed particles of which AgBr are negatively charged due to the adsorption of Br 1- ions. At reverse order merging formed dispersed particles of AgBr adsorb Ag 1+ cations and charge as a result positively.

To get a more realistic idea of ​​hydrosols and the structure of dispersed phases, let us turn to their characterization from the point of view of electrochemistry.

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Rice. 8. Scheme of the structure of the dispersed phase in an aqueous medium containing electrolytes. 1 - cations in the crystal lattice of the dispersed phase; 2 - anions in it; 3 - anions protruding at the corners with unsaturated valences; 4 - adsorbed cations of the ion swarm; 5 - dipoles H 2 O (partially deformed)

On fig. 8 schematically shows a colloidal particle surrounded by a dispersion medium, in this case water, containing Na 1+ , K 1+ , Ca 2+ , Mg 2+ , Cl 1- , 2- and other ions commonly found in soil waters that contain some amount of dissolved salts. The dispersed particle itself, as in the previous case, is shown in the form of a crystalline phase, which should have incomplete saturation with valences at the corner points. Consequently, these protrusions will accumulate adsorbed ions, in our case, the cations Na 1+ , K 1+ , NH 4 1+ , Mg 2+ , Ca 2+ , positively charging the dispersed particle and forming a diffuse layer.

The anions protruding at the corners of the lattice exert their influence not only on the ions in solution, but also on the electrically neutral water molecules. As we will later learn, the H 2 O molecule is a dipole and has an original structure. It can be represented as a single O 2- oxygen ion, the negative charge of which is neutralized by two H 1+ protons embedded in it. Both protons are located on one side (from the center of the oxygen ion), which is positively charged, and the opposite side is negatively charged. This structure of the H 2 O molecule allows it to orient itself in a certain way (Fig. 8): with the side opposite to the two H 1+ protons, it is attracted to the cations. Since electrically neutral H 2 O molecules do not neutralize the cation charge that affects them, this charge extends further, to the next nearest H 2 O molecules, which are also oriented.

Thus, a whole swarm of ions and oriented H2O molecules is established around a dispersed particle (Fig. 8). The thickness of the water shell depends on the type of hydrated cations (retaining H 2 O molecules). Cations are most strongly hydrated alkali metals. For example, the Na 1+ ion in an aqueous medium is capable of holding 60-70 oriented H 2 O molecules, while Ca 2+ is only up to 14 H 2 O molecules.

It should also be noted that in some cases, when exposed to acids, the cations of the diffuse layer can be replaced by anions, for example: Cl 1-, 2-, etc. The latter, like cations, can be hydrated; however, the orientation of water molecules in this case will be reverse to what takes place for cations (see the right side of Fig. 8).

From all that has been said, the following conclusions can be drawn:

1. From an electrochemical point of view, a charged dispersed phase can be considered a large ion ("macroion"), capable of moving in sols when an electric current is passed towards one or another electrode (electrophoresis phenomenon).
2. The dispersion medium for the dispersed phase is by no means a solvent in the usual sense of the word, although it can and usually does contain certain compounds dissociated into ions.
3. The cations of the diffuse layer can be replaced by others if, for any reason, the composition and concentration of electrolytes in the dispersion medium change. Mutual replacement or displacement of some ions by others in adsorbents (adsorbing colloids) occurs according to the law of mass action.

The described phenomena of unsaturated valencies on the surface of dispersed particles and the related adsorption from a solution of cations or anions, without any doubt, should also take place for large crystals or crystalline grains. But if we approach this issue from the point of view of the energetics of phenomena, we will find a colossal difference between real crystals and dispersed phases.

Since the phenomena of adsorption in colloids are confined to the boundaries between the dispersed phases and the dispersion medium, the total surface of dispersed particles per unit volume is very important for expressing the total energy surface of a substance. This surface is called specific surface, increases sharply as the degree of dispersion of the substance increases. This is easy to show.

Suppose we have a cubic crystal of some mineral with an edge equal to 1 cm. Its total surface will be 6 cm 2 (specific surface-6). If we divide this cube into eight parts, as shown in Fig. 9, then the total surface of the eight small cubes obtained will already be 12 cm 2, and when divided into cubes with an edge of 1 mm, 60 cm 2. If we bring further division to cubes with an edge of 1 mμ, i.e., to the size of the colloidal dispersed phase, then the total surface will reach a huge value of 6000 m 2 with a total mass volume of 1 cm 3 (i.e., the specific surface will be equal to 6 10 7). In this case, the number of cubes will reach the figure 10 21 .

Thus, between the specific surface X and grain size at we have an inversely proportional relationship, expressed by a simple formula: x = 6/y. This dependence is easy to depict in the form of a graph (Fig. 10).

It can be seen from the data presented that for coarse-grained systems, the specific surface area, and hence the surface energy associated with it, are so negligible that the latter can practically be neglected. On the contrary, in colloidal systems it acquires exceptional significance. It is because of this that a number of physical and chemical properties colloidal formations, widely used for practical purposes, is very different from the properties of coarse-grained substances.

Diffusion phenomena in colloidal solutions are incomparably weaker than in true solutions, which is explained by the much larger size of the particles of the dispersed phase compared to ions. This circumstance is reflected in the fact that mineral masses formed from colloidal solutions often have extremely heterogeneous composition and structure.

Crystal sols, i.e., typical crystalline media containing some substance in the form of a dispersed phase are often formed as a result of the crystallization of hydrosols. The process of their formation can be compared with the crystallization (transformation into ice) of turbid water, i.e., water containing dispersed particles in a suspended state. The resulting ice will also be cloudy, i.e., contaminated with the same dispersed phase that was also present in the water. In other words, it will be a crystal sol.

This primarily includes many minerals colored in one color or another, usually observed in the form of colorless transparent crystals. These are, for example, reddish carnallite, red barite (due to the content of iron oxide in the form of a dispersed phase), black calcite, the color of which in some cases is due to finely dispersed sulfides in it, in others - organic substances, etc. This should also be milky-white quartz, calcite, etc., in which finely dispersed gases or liquids, often visible in thin sections under a microscope, play the role of a dispersed phase. There are crystals, such as quartz, calcite and other minerals, with a crystal-zonal structure, due to the alternation of transparent and colored or milky-white zones.

There is no doubt that crystal sols also exist among opaque minerals. This is evidenced by the impurities of such elements that are captured by chemical and spectral analyses, which cannot be explained from the crystal chemical point of view as the result of isomorphic impurities. Such, for example, are the facts of copper content in pyrite crystals, gold in pyrite, galena, arsenopyrite, etc. Microscopic studies of polished sections prepared from such crystals, at high magnifications, often reveal the smallest inclusions of chalcopyrite, native gold, etc., suggestive about the fact that they probably contain more finely dispersed particles that are not captured using conventional microscopes*.

* (The resolution (limit of visibility) of modern conventional microscopes is 0.5-1.0 μ. Smaller particles are not captured at all by any magnification.)

Hydrogels in natural conditions are often formed from hydrosols by coagulation or, as they say, their coagulation, expressed in the formation of clots in the aquatic environment. The coagulation process occurs only when, for one reason or another, dispersed particles lose their charge, becoming electrically neutral. In this case, the forces of repulsion of particles from each other disappear, the particles combine into larger bodies, called polyions, with their subsequent settling under the action of gravity.

Neutralization of the charges of dispersed particles, causing coagulation, can be obtained in various ways:

• a) by adding electrolytes (ionic solutions) to the colloidal solution, and, depending on the charge of the dispersed phase, neutralization will be carried out by anions or cations of the electrolyte; in this way, many silty sediments are formed at the mouths of large rivers that carry colloidal solutions; last meeting with sea ​​waters containing dissolved salts, which play the role of electrolytes, undergo coagulation and precipitation in the coastal zones of marine basins;
• b) by mutual neutralization of colloidal solutions containing oppositely charged colloidal particles and taken in the corresponding quantitative relations; as a result, mixed gels are obtained (for example, brown iron ore rich in colloidal silica);
• c) by spontaneous coagulation of colloidal solutions over time, especially if the system loses the dispersion medium (water) due to its evaporation; in this case, naturally, an increase in the concentration of electrolytes contained in colloidal solutions occurs; an example is the silt and mud in drying lakes;
• d) during the circulation of colloidal solutions through capillaries in rocks; due to the high dielectric constant of water, the wetted capillary walls are negatively charged with [OH] 1- ions, which causes the precipitation of positively charged particles from circulating colloidal solutions in the form of flakes or raids; an example is the often observed "ferruginization" of limestones and other rocks, which is expressed in the coloration of the rock from the surface or along cracks with flocculent iron hydroxides in a brown color;
• e) during the processes of metasomatism (replacement) of certain rocks that easily react with chemically active solutions of salts with the formation of colloidal solutions, immediately coagulating (for example, the formation of malachite due to vitriol water in limestones), etc.

Gels of organic origin are widespread in the biosphere. The formation of gels in some cases is associated with the vital activity of bacteria. For example, it has been established that the so-called iron bacteria, processing silty lake sediments, gradually deposit colloidal iron hydroxides (limonite).

Colloids in which dispersed particles have the ability to be clothed from the surface with a layer of water molecules are called hydrophilic, and otherwise - hydrophobic. Hydrophilic colloids are much more difficult to coagulate than hydrophobic ones. In the case of coagulation of hydrophilic colloids, slimy, glue-like, gelatinous gel precipitates are usually formed.

From hydrophobic colloidal solutions, gels are most often formed in the form of powdery and flaky masses.

Gels, especially those that arise from hydrophilic colloids, easily lose water (dispersion medium) over time, i.e. undergo dehydration. Hydrogels rich in water have an almost liquid consistency at the time of formation. As the dispersion medium evaporates when standing in air, they become more elastic and, finally, hard and brittle. However, water can be completely removed only by calcination.

Some gels, when a dispersion medium is added, can not only swell (like gelatin), but also turn into sols again. This process of converting gels to sols is called peptization. Such gels are called reversible and are widely represented among the organic world. On the other hand, almost all inorganic colloidal formations belong to the category of irreversible, i.e., not converting to a sol, gels.

The phenomenon of adsorption in gels, of course, retains its significance. However, in many cases there is selective, i.e. selective, adsorption. For example, clay substances have the ability to adsorb mainly cations of potassium and radioactive elements, and manganese dioxide gel - cations Ba, Li, K (but does not adsorb anions), etc.

Thus, colloids, as we have seen, differ significantly in their properties both from true solutions and from coarse systems (with particles larger than 100 mμ). In colloids, it is not the vectorial properties of crystal lattices, not the forces of chemical affinity that come to the fore, but the enormous surface energy and the electrical forces associated with it. Nevertheless, there are gradual transitions between colloidal and true solutions, just as there are gradual transitions to coarse dispersions.

W. Ostwald gave the following scheme of dispersed systems:

Scheme of disperse systems by W. Ostwald

This scheme should equally apply to both liquid and solid systems.

At present, it is precisely established that "the colloidal state is the general state of matter" (Weimarn), i.e., any substance can be obtained in the form of a colloid. It is important to emphasize that colloids can form at a wide variety of temperatures and pressures and under a wide variety of conditions.

From a strictly theoretical point of view, colloids cannot be considered as independent special minerals, since they are essentially mechanical mixtures. various substances(dispersed phase and dispersion medium). However, according to purely external features, that is, macroscopically, they are completely indistinguishable from typical minerals. It is not possible to establish differences between them and minerals in the strict sense of the word also by the microscopic methods of research available to us. Therefore, in the courses of descriptive mineralogy, colloidal formations are conditionally considered along with typical minerals.

Previously, solid colloids (gels) were classified as amorphous minerals, since they are not observed in the form of clearly crystalline formations (if crystalline sols are not taken into account). However, x-ray studies of these substances often show that they are cryptocrystalline substances and therefore cannot be classified as typical amorphous homogeneous bodies, despite the fact that they are very similar in appearance.

About the recrystallization of gels. It has been established that hydrogels formed as a result of coagulation undergo aging over time, i.e., a gradual change in their composition and structure. This change is primarily expressed in the fact that the substance gradually loses water, i.e., undergoes dehydration (dehydration).

Such, for example, are silica hydrogels widely distributed in nature - opals. Water-rich silica hydrogels have the consistency of semi-liquid mass-jellies. With the gradual loss of water, they become more and more hard, vitreous or semi-matt when broken. This is what naturally occurring opals look like, in most cases poor in water. These formations are characterized by the finest porosity, imperceptible to the eye and under the microscope, which can only be established by staining them with any organic substances. The remaining water in them can only be removed by heating.

In the case of a strong manifestation of dehydration in water-rich gels, porosity is noticeable to the eye, and sometimes wrinkling of the mass or the appearance of characteristic drying cracks in the form of grids is observed, as is often the case when mud dries in puddles.

The study of typical solid and semi-solid gels using X-rays by the Debye-Scherrer method shows that many of them do not give interference fringes, while aged colloidal formations show a clearly crystalline structure of the substance. In a number of cases, this can also be verified by examining such gels under a microscope. Such, for example, are many stalactite formations of calcium carbonate. In place of opals (solid silica hydrogels), as a result of recrystallization, cryptocrystalline aggregates of anhydrous chalcedony or quartz are formed. Flints and agates are examples. Gels that have passed into crystalline-granular aggregates are called metacolloids(former colloids).

The essence of gel recrystallization is expressed in the combination of randomly oriented dispersed phases into larger units with a single crystal lattice. This phenomenon is known as collective crystallization. It expresses the natural tendency of substances to take on a state with the smallest specific surface and, consequently, with the smallest surface energy.

In this case, often, especially in kidney-shaped gel masses, fine-fibrous aggregates arise with a radial arrangement of individuals, which is well observed at the fracture. On the peripheral parts of crusts, spherical and kidney-shaped formations, for some minerals in these cases, crystalline facets are characteristic, which terminate radially growing individuals.

The factors affecting the recrystallization of gels are varied. Temperature and pressure are of the most significant importance, the increase of which accelerates the process of recrystallization. Climatic conditions also play an undoubted role: in areas with a dry and hot climate, dehydration and recrystallization of hydrogels formed on the surface are much more pronounced than in areas characterized by a temperate and humid climate. Of indisputable importance, of course, is the time during which, under the most diverse geological conditions, the gradual transformation of gels into clearly crystalline aggregates takes place.

Text: Svetlana Rakutova

Is it possible to treat the body with ordinary mineral water, what are the healing properties of mineral water and how is mineral water useful for children?

Properties of mineral water

We love to drink mineral water not only because we like its taste, but also because we understand that drinking mineral water is good for health. Beneficial features mineral water is due to the fact that it contains dissolved minerals found in groundwater. The same properties are possessed by water, which is taken from springs or raised from village wells. Carbonated mineral water also contains natural gases, or it may be artificially carbonated with carbon dioxide. Different countries set different standards for the amount of minerals needed for bottled water to be called "mineral".

One of the most valuable properties of mineral water is the absence of extra calories. Drinking mineral water is a way to provide the body with useful trace elements without gaining weight. Carbonated mineral water usually contains calcium, magnesium, potassium and sometimes sodium. These are the most common minerals in groundwater. Some types of carbonated mineral water contain chromium, copper, zinc, iron, manganese, selenium and other beneficial trace elements, each of which is of great importance for health. Mineral water is a better source of minerals than any other water, such as that taken from a well. In some countries with modern water filtration systems, people can drink it from the tap. But, of course, it cannot be compared in properties with mineral water. And in our country tap water most often contains fluorine and chlorine, which can adversely affect the health of many people.

If we compare the properties of mineral water with the properties of distilled water, then the latter does not contain minerals at all. Like many brands of filtered water sold in stores, it also has very little or no minerals.

The healing properties of mineral water

When talking about the healing properties of mineral water, they usually remember the content of a large amount of calcium in it. Mineral water can be an alternative source of calcium for people with lactose intolerance. Such people are unable to consume most dairy products due to their illness. But instead of milk, they can drink mineral water. Calcium in it, of course, is not as much as in dairy products, but still. Moreover, the absorption of calcium obtained from mineral water is quite comparable with the absorption of calcium from dairy products.

A very important healing property of mineral water is its ability to reduce cholesterol levels in the body. Drinking carbonated water can reduce the amount of low-density lipoprotein, the so-called "bad" cholesterol in the body, and vice versa, increase the amount of "good" cholesterol - high-density lipoprotein. These data are supported by studies conducted in 2004 on a group of older (postmenopausal) women who drank sodium-rich carbonated mineral water.

Finally, another healing property of mineral water is hydration, that is, moisturizing the body. An adult usually needs about 3 liters of water per day, and more on hot days or during active sports. At the same time, the average person does not think much about such issues and does not drink ordinary water so often during the day. And carbonated mineral water, encouraging a person with its taste, will provide the required level of hydration of the body.

Table mineral water

The composition of table mineral water depends very much on the specific brand. but General characteristics they certainly have. First of all, any table mineral water does not contain fat and calories. Many people don't consider the calorie content of drinks like coca-cola or fruit juices. Uncontrolled consumption of such drinks may well derail a weight loss program. Moreover, reducing the amount of "liquid calories" can lead to weight gain, in contrast to reducing the intake of calories from food. Here the choice is obvious in favor of table mineral water, the use of which will always keep calories under control.

Almost all brands of table mineral water, except for calcium and sodium, also contain magnesium. This trace mineral is essential for bone health, and it also supports the development of cells, muscle and nerve tissue. Ordinary table mineral water contains up to 41% of the daily recommended intake of magnesium. Remember that you should strive to ensure that the daily intake of magnesium and other trace elements is carried out not only from table mineral water, but also from food.

Mineral water for children

Parents face difficult choices when it comes to deciding on the healthiest drink to fit into a balanced diet for a child. Faced with a dense stream of advertising information offering thousands of different brands of delicious drinks for children, the child hardly agrees to drink plain water. It is impossible to convince a small child that this is good for health, the main thing for him is that it is “tasty”. However, plain mineral water for children is much healthier than sweet fruit sodas or milkshakes.

It is worth noting here that mineral water enriched with carbon dioxide is not at all useful for children. Carbonated water and carbonated soft drinks have a long-term effect negative impact on the health of the child. Manufacturers saturate carbonated mineral water for children not only with phosphorus and carbonic acid, to create bubbles, but also with various flavorings - various man-made sweeteners that are more harmful than ordinary sugar extracted from fruits. The use of carbonated mineral water for children for a long time leads to a decrease in the level of calcium in the child's body. This can weaken the roots of the teeth and cause plaque damage. And excess sugar puts children at risk of developing diabetes.

The physical properties of minerals are determined by their internal structure and chemical composition. Physical properties include density, mechanical, optical, magnetic, electrical and thermal characteristics, radioactivity and luminescence.

The density of a mineral is the weight of a unit of its volume. The density depends on the atomic weight of the atoms or ions that make up the crystalline substance, and on the density of their packing in the crystal lattice of the mineral. In natural substances, it varies widely: from values ​​less than 1 g/cm 3 to 23 g/cm 3 . By density, minerals are divided into light (up to 2.5 g / cm 3), medium (2.5-4.0 g / cm 3), heavy

(4.0-8.0 g / cm 3) and very heavy (more than 8.0 g / cm 3). Light are oils, coals, gypsum, halite; quartz, calcite, feldspars are classified as medium, ore minerals are classified as heavy.

To assign a mineral to one of these groups, it is enough to determine its density approximately - by weighing it in the palm of your hand.

Mechanical properties include hardness, cleavage, fracture, brittleness, malleability, flexibility.

Hardness mineral - this is the degree of its resistance to external mechanical influence (scratching, etc.). It is estimated on a ten-point scale of relative hardness proposed by the German scientist F. Moos in 1811. Relative hardness is determined by scratching the studied mineral with sharp edges of reference minerals (passive hardness) or reference minerals of the studied (active hardness). Standard minerals, the hardness of which (in conventional units) corresponds to their numbers, are located on the Mohs scale as follows: 1 - talc, 2 - gypsum, 3 - calcite, 4 - fluorite, 5 - apatite,

6 - orthoclase, 7 - quartz, 8 - topaz, 9 - corundum, 10 - diamond.

If, for example, gypsum does not leave scratches on the surface of the studied mineral, but calcite does, then its hardness is 2.5.

In the practice of field work, in the absence of the Mohs scale, the hardness of minerals is determined using common objects with known hardness. For example, for a pencil it is 1, for a nail it is 2-2.5, for a yellow coin it is 3-3.5, for glass it is 5, for a steel rod (nail) it is 6. Most natural compounds have a hardness of 2 to 6.

In laboratory studies, the determination of the hardness of a mineral should begin with checking whether it scratches glass, and not vice versa, so as not to spoil the samples. Then clarify the value of hardness (if necessary) using the minerals of the Mohs scale.

Cleavage - the ability of crystals and crystalline grains to split or split along certain crystallographic directions with the formation of even shiny surfaces, called cleavage planes. There are cleavages:

very perfect - minerals (micas, chlorite) are easily split along the bedding planes into the thinnest leaves, forming mirror-shiny cleavage planes;

perfect - minerals (calcite, halite, feldspars) upon impact split along cleavage, and the resulting knockouts repeat the crystal in shape;

middle - on the chips of minerals (feldspars, pyroxenes), both cleavage planes and uneven fractures in arbitrary directions are observed;

imperfect - mineral grains are limited by irregular surfaces, with the exception of individual crystal faces (sulfur, olivine);

very imperfect (or there is no cleavage) - the mineral always splits along arbitrary uneven surfaces, sometimes forming a characteristic fracture (quartz, corundum, magnetite).

Minerals that lack cleavage have separateness.

separateness - this is the ability of a mineral to split only in certain areas, and not along certain planes. Separation cracks are coarser, not completely flat, their orientation depends on the nature of the distribution of inclusions, twinning, etc.

kink- the shape of the surface formed during the splitting of minerals. The nature of the fracture depends on the cleavage. Distinguish between smooth and uneven, stepped, conchoidal and finely conchoidal, splintery, granular and rough, hooked, and other types of fractures.

An even fracture passes along the cleavage planes. stepped a fracture is observed in minerals with perfect cleavage; uneven and conchoidal (similar to the surface of shells) - in minerals with imperfect and very imperfect cleavage. A fracture is considered splintery, the surface of which is covered with oriented splinters, which are grains of elongated crystals (hornblende, gypsum). Grainy a fracture occurs in minerals with an isometric (or close) appearance of crystals (halite). Fine aggregates with a matte surface (limonite, kaolinite) have an earthy fracture, and native metals have a hooked fracture.

Brittleness, malleability, flexibility minerals are determined visually, by their reaction to mechanical stresses.

Optical properties include the color of the minerals, the color of the streak, the degree of transparency, and the brilliance.

Color(color) of the mineral is an important diagnostic feature. The names of many minerals are given by their color (for example, chlorite in Greek means "green", albite - from Latin "white", ruby ​​- "red"). In natural compounds, the color of the mineral is due to the following reasons:

the presence of a dye element (chromophore) in the composition of the mineral. The most important chromophores are Cu, Ni, Co, Ca, Mn, Fe;

the presence of finely dispersed mechanical colored impurities, which can be of both organic and inorganic origin (brown iron oxides, black manganese oxides, etc.);

the presence of submicroscopic oriented inclusions and internal surfaces of cleavage cracks. In some minerals, in addition to the main color, sometimes bright blue, light blue or greenish tints flare up on cleavage planes or polished surfaces at certain angles of rotation. Such phenomena are called iridescence. This phenomenon is observed most often in plagioclases (labrador);

the presence of variegated surface formations, the so-called. tint, for example, golden films are observed on the surface of brown iron ore, dark yellow or variegated - on the surface of chalcopyrite.

In laboratory classes, the color of minerals is determined by eye, by comparison with known colors.

Dash color is the color of the mineral in fine powder. This sign, in comparison with the color of minerals, is a more constant and, consequently, more reliable diagnostic feature.

The color of the line does not always match the color of the mineral itself. For example, in magnetite both the color and color of the streak are black, while in hematite, which in dense aggregates has a steel-gray or black color, the streak is cherry red. Most light-colored and transparent minerals have a colorless streak.

In practice, the trait is determined using an unglazed porcelain plate - a biscuit. The powder is obtained in the form of a trace on the plate, if you draw a mineral on it. The line on the biscuit is left by minerals with a hardness of up to 6 (6 is the hardness of the biscuit). Harder minerals do not leave lines, but scratch the biscuit. For them, the trait is not defined.

Transparency The property of minerals to transmit light through them is called. According to the degree of transparency, minerals are divided into 3 groups:

transparent - minerals that transmit light in plates of any thickness (rock crystal, Icelandic spar);

translucent - minerals that are translucent only in thin plates (opal, chalcedony);

opaque - do not transmit light even in the thinnest plates (ore minerals).

Shine- the ability of a mineral to reflect the light flux incident on it. Smooth surfaces (faces, cleavage planes) always reflect light better than uneven ones. There are the following types of gloss:

metallic - the strongest luster of minerals. It is observed in dark-colored opaque minerals. Visually similar to the luster of an unoxidized metal surface. Native metals have such brilliance.

semi-metallic (metallic) - a luster reminiscent of the luster of a tarnished surface of metals. Observed in hematite, graphite.

diamond - the strongest brilliance of light-colored minerals. An example is the brilliance of diamonds, sulfur on the faces of crystals.

glass - the most common luster of light-colored and colorless minerals. Such a shine is found in quartz (on the faces), halite, carbonates and sulfates.

If the mineral in a fracture has a hidden tuberculate or pitted surface, the light is scattered randomly upon reflection, creating a greasy sheen. For cryptocrystalline masses (chalcedony) and solid light-colored gels (opal), the surfaces of which have a more pronounced roughness, a waxy sheen is characteristic. Finely dispersed masses with fine porosity have a matte sheen. In this case, the incident light is very strongly scattered upon reflection and the surface of the mineral appears dull (kaolinite, iron hydroxides).

For minerals with a pronounced orientation of the elements of the structure, silky and mother-of-pearl luster is characteristic. Silky sheen is found in minerals with a parallel-fibrous structure (asbestos, gypsum selenite), mother-of-pearl - in transparent minerals with a layered structure (mica, talc).

Magnetic properties are a set of properties that characterize the ability of minerals to be magnetized in an external magnetic field. In practice, the testing of the magnetism of minerals is carried out using a mining compass. Magnetic minerals (magnetite) deflect the arrow from its natural direction (north).

Electrical properties - this is a set of properties that characterize the ability of minerals to conduct an electric current.

Minerals have a set of physical properties by which they are distinguished and defined. Let's consider the most important of these properties.

Optical properties. Coloring or color mineral is an important diagnostic characteristic. Some minerals have a certain color, by which it can be almost unmistakably determined. The color of other minerals can vary widely within a single mineral individual. The color of minerals depends on their chemical composition, internal structure, mechanical impurities and, mainly, on chemical impurities of chromophore elements: Cr, V, Ti, Mn, Fe, Al, Ni, Co, Cu, U, Mo, etc.

By color, all minerals are generally divided into dark-colored and light-colored. When characterizing the color of a mineral for diagnostic purposes, one should strive for its most accurate description. When describing a color, complex definitions are used, for example, bluish-green, milky-white, etc., the main color in such adjectives is in second place.

Mineral color in powder, or stroke color , is also an important characteristic that sometimes plays a decisive role in determining the mineral. The color of a mineral in powder can differ significantly from the color of a mineral aggregate in a piece. To determine the color of a mineral in powder, the mineral is carried out over the rough surface of a porcelain plate, cleaned of enamel. Such a plate is called a biscuit (from French Biscuite - unglazed porcelain). It is on it that the line remains that allows you to evaluate the color of the mineral in the powder. However, if the hardness of the mineral exceeds the hardness of the biscuit, it is impossible to obtain a trait in this way.

Transparency- the ability of minerals to transmit light without changing the direction of its propagation. Transparency depends on the crystal structure of the mineral, the intensity of its color, the presence of finely dispersed inclusions and other features of its structure, composition and formation conditions. According to the degree of transparency, minerals are divided into: transparent, translucent, translucent, opaque.

Transparent- transmit light throughout the volume. Through such minerals one can see like through a window pane.

translucent- only the outlines of objects are visible through them. Light passes through the mineral, as through frosted glass.

translucent- transmit light along a thin edge or in thin plates.

Opaque- do not transmit light even in thin plates.

Other things being equal, finer-grained aggregates appear less transparent.

Shine- the ability of a mineral to reflect light. Reflection of light from the surface of a mineral is perceived as a luster of varying intensity. This property also depends on the structure of the mineral, its reflectivity and the nature of the reflective surface. There are the following types of gloss.

Metal- a strong luster characteristic of native metals and many ore minerals.

metallic or semi-metallic- reminiscent of the luster of a dull metal surface.

Diamond shine (the brightest) is characteristic of diamond, some varieties of sphalerite and sulfur.

Glass- is quite widespread and resembles the shine of glass.

Fatty- gloss, in which the surface of the mineral is as if covered with a film of fat or oiled. Oily sheen occurs due to the irregularities of the fracture surface or the face of the mineral, as well as due to hygroscopicity - the absorption of water with the formation of a water film on the surface.

Wax- in general, it is similar to fatty, only weaker, dull, characteristic of cryptocrystalline mineral aggregates.

Pearl- resembles the iridescent sheen of the surface of a mother-of-pearl shell.

Silky- observed in aggregates having a fibrous or needle structure. It resembles the sheen of silk fabric.

Matte luster is characteristic of fine-grained aggregates with an uneven earthy surface. Matte gloss practically means no shine.

Sometimes the brilliance on the crystal faces, on its cleavage and on the cleavage surface may differ, for example, in quartz, the brilliance on the faces may be glassy, ​​while on the cleavage it is almost always greasy. As a rule, the luster on cleavage surfaces is brighter and more intense than on crystal faces.

Mechanical properties. Cleavage - the ability of a mineral to split in certain directions with the formation of relatively smooth surfaces (cleavage surfaces).

Some minerals, when exposed to them, are destroyed along regular parallel planes, the direction and number of which are determined by the characteristics of the crystal structure of the mineral. Destruction occurs preferably in those directions in which the weakest bonds exist in the crystal lattice. The nature of cleavage is established by studying individual mineral grains. Amorphous minerals do not have cleavage.

According to the ease of splitting and the nature of the surfaces formed, several types of cleavage are distinguished.

Very perfect cleavage- the mineral without much effort splits or splits by hand into thin plates. Cleavage planes are smooth, even, often mirror-smooth. Very perfect cleavage usually appears in only one direction.

Perfect cleavage- the mineral is easily split by a weak blow of a hammer with the formation of smooth shiny planes. The number of cleavage directions varies for different minerals (Fig. 8).

Average cleavage- the mineral breaks upon impact into fragments, limited approximately to the same extent by both relatively even cleavage planes and irregular fracture planes.

Imperfect cleavage– splitting of the mineral leads to the formation of fragments, most of which is limited by uneven fracture surfaces. Recognition of such cleavage is difficult.

Very imperfect cleavage, or lack of cleavage, - the mineral splits in random directions and always gives an uneven fracture surface.

The number of cleavage directions, the angle between them, the degree of its perfection are among the main diagnostic features in determining minerals.

Rice. 8. Perfect cleavage:

a – cleavage punches – halite cube, calcite rhombohedrons; b – visible cracks developed along the cleavage directions; c - different orientation and number of cleavage planes: 1 - cleavage in one direction, mica; 2 - cleavage in two mutually perpendicular directions, orthoclase; 3 - cleavage in two non-perpendicular directions, amphibole; 4 - cleavage in three mutually perpendicular directions, halite; 5 - cleavage in three non-perpendicular directions, calcite; 6 - cleavage in four directions parallel to the faces of the octahedron, diamond; 7 - cleavage in six directions, sphalerite

kink- the type of surface formed during the splitting of a mineral. This characteristic is especially important in the study of minerals with imperfect and very imperfect cleavage. For such minerals, the appearance of the fracture surface can be an important diagnostic feature. There are several characteristic types of fracture.

In some minerals, a characteristic concave or convex concentric-ribbed surface may appear at a fracture, resembling a shell in shape. Such a break is called conchoidal. Most often, the mineral splits on an uneven surface that does not have any characteristic features. Such a break is called uneven, it is possessed by many minerals devoid of cleavage. Native metals, copper, iron and other minerals are found hooked fracture; native silver has chopped break. Minerals with perfect cleavage in 1-2 directions give smooth break. In addition, the break can be stepped, splintery, grainy.

Hardness- the ability of a mineral to resist external mechanical stress - scratching, cutting, indentation. This feature, like most others, depends on internal structure mineral and reflects the strength of bonds between lattice sites in crystals. In the field, the relative hardness of minerals is determined by scratching one mineral with another.

To assess the relative hardness of a mineral, an empirical scale is used, proposed at the beginning of the last century by the Austrian mineralogist F. Moos (1772-1839) and known in mineralogy as the Mohs hardness scale (Table 1). The scale uses ten minerals of known and constant hardness as standards. These minerals are arranged in order of increasing hardness. The first mineral - talc - corresponds to the lowest hardness, taken as 1, the last mineral - diamond - corresponds to the highest hardness of 10. Each previous mineral of the scale is scratched by the next mineral.

Table 1 - Mineral hardness scale

The Mohs scale is a relative scale, the increase in hardness within it occurs very unevenly from standard to standard, for example, the measured absolute hardness of diamond is not 10 times greater than the hardness of talc, but approximately 4200 times. The absolute value of hardness increases with decreasing radii and increasing the charge of the ions that make up the crystal. To determine the relative hardness of the mineral on its fresh (non-weathered) surface with pressure, an acute angle of the reference mineral is drawn with pressure. If the standard leaves a scratch, then the hardness of the studied mineral is less than the hardness of the standard, if it does not leave a scratch, the hardness of the mineral is greater. Depending on this, the next standard is selected higher or lower on the scale until the hardness of the mineral being determined and the hardness of the reference mineral coincide or are close, i.e. both minerals do not scratch each other or leave a faint mark. If the studied mineral is between two standards in terms of hardness, its hardness is defined as intermediate, for example 3.5.

For an approximate assessment of the relative hardness of minerals in the field, you can use a simple pencil lead (hardness 1), fingernail (2-2.5), copper wire or coin (3-3.5), steel needle, pin, nail or knife (5 -5.5), glass (5.5-6), file (7).

Density minerals varies from 0.8-0.9 (for natural crystalline hydrocarbons) to 22.7 g / cm 3 (for osmic iridium). The exact determination is carried out in the laboratory. By density, all minerals can be divided into three categories: light - density up to 2.5 g / cm 3 (gypsum, halite), medium - density up to 4 g / cm 3 (calcite, quartz, feldspars, micas) and heavy - density more than 4 g / cm 3 (galena, magnetite). The density of most minerals is from 2 to 5 g/cm 3 .

The mechanical properties that can be used as diagnostic features of minerals also include brittleness and malleability.

fragility- the property of a substance to crumble under pressure or on impact.

Ductility- the property of a substance under pressure to flatten into a thin plate, to be plastic.

Special properties. Some minerals are characterized by special, only their inherent properties - taste(halite, sylvin) smell(sulfur), combustion(sulfur, amber), magnetism(magnetite), reaction with hydrochloric acid(minerals of the carbonate class), electrical conductivity (graphite) and some others.

Magnetic properties of minerals determined by their magnetic structure, i.e. firstly, by the magnetic properties of the atoms that make up the mineral, and, secondly, by the arrangement and interaction of these atoms. Magnetite and pyrrhotite are the two most important magnetic minerals that act on the magnetic needle.

Electrical conductivity. For the most part, minerals are poor conductors of electricity, with the exception of sulfides, some oxides (magnetite) and graphite, the resistivity of which is less than 10 Ohm m. However, the overall electrical conductivity of mineral aggregates depends not only on the properties of the mineral itself, but also on the structure, and, most importantly, on the degree of porosity and water cut of the aggregate. Most minerals conduct electricity through pores filled with natural mineralized waters - electrolyte solutions.

During the repair or construction of the premises, one has to deal with many contentious issues. One of the main choices building materials. You need to evaluate the pros and cons of your preferences, compare with analogues and make a worthy decision. Mineral wool has gained immense popularity among builders as a heater and soundproofing material.

Wall insulation is economical heating, the absence of fungi, salvation from mold and dampness. In the summer months, good insulation prevents the walls from overheating and maintains a comfortable temperature in the room.

What is mineral wool?

Mineral wool is an economical insulation made of natural non-combustible materials. Its manufacture occurs by exposing basalt fiber and metallurgical slags to high temperatures. It has good fire-fighting properties, which is especially important in the construction of houses with stove heating and in hazardous industries.

Scope of application

insulation of facades and attic;

internal wall insulation;

insulation of hot structures in production;

in the heating system, in the construction of pipelines; in the construction of flat roofs.

Such widespread use is possible due to the various technical characteristics of mineral wool. It has several varieties, differs in the structure of the fibers. Each type is distinguished by its thermal conductivity and moisture resistance.

Types of mineral wool

glass wool

It is obtained from broken glass and small crystalline materials. Fiberglass is distinguished by a good coefficient of thermal conductivity - 0.030-0.052 W / m K. The length of its fibers is from 15 to 55 mm, the thickness is 5-15 microns. Working with glass wool requires extreme caution. By its properties, it is prickly, broken threads can penetrate the eyes and damage the skin. Therefore, gloves, goggles, and a respirator are required to work with the material. It is optimal to heat glass wool up to 450 degrees, do not cool - below 60 degrees. The positive properties of glass wool are good strength and elasticity, easy installation, and the possibility of trimming.

slag wool

The fibers of this blast-furnace slag product are about 16 mm long. The high hygroscopicity of this raw material does not allow the use of slag wool in the insulation of facades, heating mains. Most often it is used for insulation of non-residential buildings. Heating temperature 250-300 degrees. According to these and other properties, it is inferior to other types of mineral wool. Its main advantage is low price, easy installation, reliable sound insulation.

stone wool

It is she who is the highest quality type of mineral wool. In size, its sheets are not inferior to slag fiber. But it is not prickly, very easy to use. It has a rather high coefficient of thermal conductivity; this fiber can be heated up to 1000-1500 degrees. When heated above the permissible degrees, it will not burn, but only melt. When we talk about modern material for warming houses, we mean just this type of wool - it is also called basalt.

Internal wall insulation

Production and properties of basalt wool

A bit of history:

For the first time, thin filaments of volcanic rock were discovered in Hawaii. After the volcanic eruption, scientists drew attention to interesting finds. The red-hot lava flew up, and the wind pulled the rocks into thin threads, which solidified and turned into lumps, similar to modern mineral wool.

Production of basalt insulation

Due to heat treatment at fairly high temperatures, rock materials are converted into fibrous material. After that, binding components are added to them and put under pressure. Next, the fiber enters the polymerization chamber, where it turns into a solid product.

Basalt insulation can have a high density, which gives the product additional rigidity and good load resistance. porous structure Helps absorb impact noise. During the production process, you can get cotton wool of various structures. A more flexible one is used in pipelines, a semi-rigid one is insulated at home, and a rigid structure is indispensable in production.

Properties of mineral wool from basalt:

soundproofing;

high thermal insulation;

safety;

moisture resistance;

durability;

absolute incombustibility.

Basalt fiber is produced in rolls and slabs. It is very light and easy to cut.

Note!

Recently, the foil type of product has been very popular with builders. Thanks to the foil elevated level heat saving. It is suitable for warming any surfaces, it is this material that is used for ventilation and refrigeration systems.

Stamps

In the factory, you can get a product of various densities. It is for this property that several grades of mineral wool can be distinguished.

Brand P-75

It has a density of 75 kg per cubic meter. A product of low density is used where it is not necessary to withstand a serious load. For example, for the insulation of some roofs, attics. Also, cotton wool of this brand is used for pipes of heating mains.

Attic insulation scheme

Brand P-125

With its density of 125 kg per cubic meter, it is suitable for floor and interior wall insulation. The material has good noise protection, so it is an ideal mineral wool for soundproofing.

Brand ПЖ-175

Material with high density and good rigidity. It is indispensable where it is necessary to insulate floors made of reinforced concrete or metal.

Brand PZH - 200

It has the highest rigidity, as indicated by the indicated abbreviation. Just like PZh-175, it is used for thermal insulation of sheet metal walls. But, besides this, this brand should be used where there is an increased likelihood of a fire hazard.

Facade mineral wool

Most often, mineral wool is used to insulate facades. All of the above properties of basalt fiber are significantly superior to the same foam. It is this material that does not easily retain heat, but also helps air to penetrate to the walls. Special attention It is worth paying the very choice of product and installation of structures.

Facade insulation

Important: It is better to purchase products in the form of plates, which will greatly simplify their installation. The density of the material should not be less than 140 kg / cubic meter. The width of the plate itself is 10 cm.

Mineral wool and harm to health

The pessimism that the use of mineral wool causes serious harm to health is based on the technical characteristics of past generations of mineral wool. Indeed, constant work with glass wool was very dangerous for the lungs. Today, this product is used very rarely. Modern basalt fiber is produced using high-quality raw materials, paying great attention to the technological process. Subject to all sanitary standards, binding harmful substances - phenol and formaldehyde practically lose their negative properties for the environment.

To be sure of the safety of the material, you need to pay attention to the choice of the manufacturer. If stone wool is mined by underground organizations, without complying with GOSTs and the necessary technical conditions, then there is no guarantee that the action of phenol will not affect the health of others.