Regulations 

Chemical formula of basalt. Origin of igneous basalt rock

What characteristics do granite and basalt have, how do they differ from each other? Firstly, these breeds have different origins, and secondly, each of them has its own structure, which immediately catches the eye. Thirdly, both granite and basalt are strong, but basalt is still stronger. However, this does not mean that it is much easier. So, first things first.

Origin and appearance

In addition, fine and medium-grained minerals lend themselves well. These allow granite to retain its shape and shine even under significant loads and friction for more than a dozen years, thanks to which this durable material is so popular as a facing.

Basalt rock is heavier than granite, but also more durable. Its density is 2520-2970 kg / m³, compression resistance is up to 400 MPa. It is resistant to the action of almost any chemical substance, be it acid or alkali, as well as to temperature fluctuations, up to 1200 ° C.

It is curious to note the fact that, with its characteristics, basalt has a high plasticity. This makes it possible to manufacture modern acoustic systems from it, capturing the subtlest vibrations of sound waves. Basalt is also often used for facing works, making street monuments, mineral wool for insulating buildings, as well as getting rubble, making concrete and stone casting.

What is the difference between granite and basalt?

According to research by geologists, the main difference between them lies in their origin: almost the entire bottom of the world's oceans is covered with basalt deposits, while the rocks of the continents are formed of granite. A knowledgeable person will also distinguish them by color. The basalt rock is dark in color, rather thin, but at the same time heavy. Granite, on the other hand, is light in color, relatively light and strong, like a rock.

During the movement of the lithospheric plates of the earth's crust, the continents collide with the ocean floor, crushing it under themselves by the continental massif of rocks. At the same time, when exposed to high temperatures (over 1450 ° C), basalt melts and sinks to the bottom, while granite, on the contrary, comes out to the surface of the earth.

Basalt Is the most common natural rock, volcanic rock that can be found in the form of interstratal bodies or lava flows that have arisen after a volcanic eruption. Rich deposits are located in India, the United States and the Hawaiian Islands. The most famous basalt deposits- these are volcanoes located in Kamchatka and the Kuril Islands, as well as Vesuvius and Etna.

Description: Basalt rock with excellent characteristics

The basalt stone has a black, smoky, dark gray or greenish black color. Its composition is based on augite and feldspar.

The density of the stone is 2530-2970 kg / m 2;. Water absorption ranges from 0.25 to 10.2%. Poisson's ratio is 0.20-0.25. Specific heat 0.85 J / kg K at 0 ° C. The melting point is in the range of 1100-1250 ° C, in some instances this figure reaches 1450 ° C. The resistance is in the range of 60-400 MPa.

Chemical and mineral composition of basalt

Into the mineral basalt composition includes:

  • volcanic glass,
  • microliths of plagioclases,
  • titanomagnetite,
  • magnetite and clinopyroxene.

The structure of the mineral is porphyry, glassy or cryptocrystalline aphyric. Rocks of the first variety are distinguished by the presence of a small amount of impurities of black pyroxene prisms, as well as isometric crystals of olivine, which has a yellow-boggy hue. Such inclusions can reach a quarter of the total mass.

In addition, in basalt composition hornblende and orthopyroxene may be present. The most common accessory mineral is apatite.

Basalt is mined primarily from volcanic lava flows. Pieces extracted from the upper part can be bubbly, since during the cooling of the volcanic rock, vapors and gases come out of it. Then other minerals can be deposited in the resulting holes, the most common among them are prehnite, zeolite, calcium and copper. This type of basalt is called amygdaloid.

Practical application of basalt

Building materials made from this stone are widely used in construction because they are characterized by:

  • abrasion resistance,
  • to the influence of alkalis and acids,
  • excellent performance of thermal insulation and noise absorption, strength, heat resistance and fire resistance,
  • high dielectricity,
  • durability,
  • vapor permeability and,
  • equally important, environmental friendliness.

This mineral is used as a building stone, for the production of mineral wool, filler for concrete and stone casting. Road and facing stones are also made from it, crushed stone and acid-resistant powder are obtained. At the moment, facing plates, simultaneously with the decorative purpose, serve as insulators. Due to its resistance to weathering, basalt is well suited for finishing the exterior of buildings, as well as for casting outdoor sculptures.

Production of basalt and products based on it

Often basalt production Is a mining industry. In special quarries and mines, stone is mined, on the basis of which various products are subsequently produced.

In the form of basalt fiber, this mineral is used for insulating buildings and roofs, in three-layer sandwich panels, insulation of low-temperature equipment units for extracting nitrogen and creating oxygen columns, for heat and sound insulation of pipelines, stoves, fireplaces and other braziers, power units and in general buildings and structures for any purpose.

Basalt in molten form is used to create stair treads, shaped tiles and other building materials. Apparatuses of arbitrary shapes are cast from it, including stands for batteries, as well as insulators for networks with voltages of various sizes. Powder from this material is used for the production of extruded reinforced products.

Common types of basalt

Basalt types differ from each other in various indicators, primarily, such as color and structure. The most famous brand name is the variety called "Basaltina". This material is of Italian origin, which is mined near the capital of this country and has been used mainly for architectural purposes since the times of Ancient Rome.

Its strength is comparable to that of granite, and its decorative qualities are comparable to those of limestone. After laying, the stone retains the saturation of the color palette for a long time. Therefore, its cost is often more than twice the price of other brands.

Another variety is asiatic... It is distinguished by its dark gray color and reasonable price. It is widely used for design and architectural purposes.

Moorish green basalt has a rich dark green hue, with various inclusions present in it, which give the stone an original appearance while maintaining all physical and mechanical characteristics. Only the criteria for hardness and frost resistance are somewhat lower.

Twilight basalt is brought from China. It is smoky gray or black in color. It is recognized as the strongest and most durable and frost-resistant among all varieties of this mineral. It is well protected from negative atmospheric influences.

BASALT (Latin basaltes, basanites, from Greek basanos - touchstone; according to another version, from Ethiopian basal - iron-containing stone * English basalt, basaltic rocks; German Basalt; French basalte; Spanish basalto) - outpouring cenotypic , effusive analog. Basalt color is dark to black. Consists mainly of the main, monoclinic, and accessory minerals -, etc. Basalt structures - intersertal, aphyric, less often hyalopilitic, texture - massive or porous, amygdaloid. Depending on the grain size, they are distinguished: the coarse-grained -, the fine-grained - anamesite, the fine-grained - the basalt itself. Paleotypic analogs of basalt -.

Basalt chemical composition

Average chemical composition of basalt according to P. Daly (%): SiO 2 - 49.06; TiO 2 1.36; Al 2 O 3 - 15.70; Fe 2 O 3 - 5.38; FeO 6.37; MgO 6.17; CaO 8.95; Na 2 O - 3.11; K 2 O - 1.52; MnO 0.31; P2O5 0.45; H 2 O - 1.62. The content of SiO 2 in basalt ranges from 44 to 53.5%. According to the chemical and mineral composition, olivine unsaturated with silica (SiO 2 about 45%) and olivine-free or with an insignificant content of olivine, slightly saturated with silica (SiO 2 about 50%) tholeiitic basalts are distinguished.

Physical properties of basalt

The physical and mechanical properties of basalt are very different, which is explained by the different porosity. Basaltic magmas, having a low viscosity, are easily mobile and are characterized by a variety of forms of occurrence (, flows, stratal deposits). Basalt is characterized by columnar, less often spherical jointing. Olivine basalts are known at the bottom of the oceans, oceanic islands (Hawaii) and are widely developed in folded belts. Toleitic basalts occupy vast areas on (formations of Siberia,). Deposits of ores are associated with the rocks of the trap formation (Siberia). A deposit is known in the almond-stone basaltic porphyrites of the Upper Lake region.

Basalt density

Basalt 2520-2970 kg / m³. Porosity coefficient 0.6-19%, water absorption 0.15-10.2%, compression resistance 60-400 MPa, abrasion 1-20 kg / m², melting point 1100-1250 ° C, sometimes up to 1450 ° C, specific heat 0.84 J / kg.K at 0 ° C, Young's modulus (6.2-11.3) .10 4 Mpa, shear modulus (2.75-3.46) .10 4 Mpa, Poisson's ratio 0.20 -0.25. The high strength of basalt and the relatively low melting point have led to its use as a building stone and raw material for stone casting and mineral wool.

Basalt application

The use of basalt - basalt is widely used to obtain road (side and paving stones) and facing stones, acid-resistant and alkali-resistant material. The industry requirements for the quality of basalt as a raw material for crushed stone are the same as for other igneous rocks. For the production of mineral wool, basalt is usually used in batching. It was found that the melting temperature of the raw material should not exceed 1500 ° C, and the chemical composition of the melt is regulated by the following limits (%): SiO 2 - 34-45, Al 2 O 3 - 12-18, FeO up to 10, CaO - 22-30, MgO - 8-14, MnO - 1-3. Basalt stone materials have great chemical resistance, abrasion resistance, high dielectricity and are used in the form of floor slabs and cladding, pipeline lining, cyclones, as well as various insulators.

B for crushed stone 50 explored with industrial reserves of 40 million m³. Two basalt deposits with commercial reserves of 6.5 million m³ have been explored for facing stone (,). The annual production of basalt is over 3 million m³. In the CCCP, basalt deposits are concentrated mainly in Armenia, Eastern Siberia and the Far East. Basalt covers in the eastern regions of the United States form large deposits in the states of New York, New Jersey, Pennsylvania, Connecticut (the largest and stone crushing plants).

BASALT, a ceramic material with high mechanical, physical, electrical and chemical properties and obtained by thermal processing of rocks of the same name.

1. Basalt as a rock... Basalt, or, rather, basalts, are typical igneous (effusive) basic rocks of deep origin and young, mainly Tertiary, age. Basalt is widely known for the picturesque detachments it forms in the form of 6-sided (and sometimes 3- or 5-sided) prisms 3-4 m long with planes perpendicular to the sides (Fig. 1); it is also found in the form of natural flagstone stairs, shell-like ball joints and other extremely picturesque rocks.

Basalt is a dark-colored rock, sometimes grayish-black, sometimes with a bluish tint; sometimes it is greenish or reddish. The very name "basalt" is of ancient origin and in Ethiopian language means "dark", "black". This breed is very homogeneous in its delicate constitution. Dense and extremely hard, it has a different order of grain in different cases. Coarse and medium-grained varieties are called dolerites, fine-grained - anamesites, and very fine-grained - basalt proper. The difference in the texture of basalt with the same bulk composition is explained by the conditions for the solidification of igneous magma (cooling rate, pressure, etc.). The petrographic composition of basalt can vary significantly, but the minerals included in the composition of basalt are replaced by petrographic equivalents, as a result of which the basalt as a rock retains its habitus very steadily. Under the microscope, basalt appears as a glassy groundmass ("basis") with microfluidic composition. The base contains numerous crystals of feldspar, olivine, magnetic iron ore and other less characteristic minerals. Depending on the content of mineral inclusions cemented by the basis, basalts are distinguished: plagioclase, leucite, nepheline and melilite. Actually, it is customary to call the first basalt, i.e., containing calcareous feldspar, augite and olivine. Chemically, basalt is related to gabbro (G.) and diabase (D.). The gross chemical analysis of plateau-forming basalt is characterized, according to Washington, by the following data:

Basalt is characterized by significant radioactivity: it contains from 0.46 ∙ 10 -3 to 1.52 ∙ 10 -3% thorium and from 0.77 ∙ 10 -10 to 1.69 ∙ 10 -10% radium. Shallower basalt varieties are more acidic and gradually pass to dacites, trachytes, etc. According to the latest views, basalt is a material that forms a hard shell of the earth: under the continents 31 km thick, and under the oceans - from 6 km or more; this shell floats on a viscous-liquid underlying basalt layer ("substrate"). Thus, basalt is assumed to be everywhere. As for the surface of the earth itself, the outcrops of this rock are very numerous. Outside the USSR, they exist: in Auvergne, along the banks of the Rhine, in Bohemia, Scotland and Ireland, on the island of Iceland, in the Andes, in the Antilles, on the island of St. Elena and in various other localities. There are many basalt deposits in the northern, western and southeastern parts of Mongolia. Within the USSR, basalt is distributed in the Caucasus and Transcaucasia, as well as in the north of Siberia, in the basin of the river. Vitim. In the near future, the following deposits may be of the greatest interest: Berestovetskoye - Volyn District of the Ukrainian SSR, Isachkovsky - Poltava District of the Ukrainian SSR, Mariupol - Mariupol District of the Ukrainian SSR, Chiaturskoye, Beloklyuchinskoye, Manglisskoye and Saganlugskoye, Adjaris-Tskhalskoye - Georgian SSR, Erivan SSR Olonets diabase from the shores of Lake Onega.

2. Properties of natural basalt... The direct use of natural basalt and its further processing presuppose a sufficient knowledge of its mechanical, physical and chemical properties. However, these properties are significantly related to the composition and texture of the basalt and therefore vary significantly depending on the deposit. If we talk about basalt in general, then the properties of its m. B. are characterized only by the limits of the corresponding constants. The data presented below for basalt are partially compared with the data for diabase and gabbro. Apparent specific gravity (piece): 2.94-3.19 (B.), 3.00 (D.), 2.79-3.04 (G.). True specific gravity (powder) about 3.00 (B.). Porosity in% volume: 0.4-0.5 (B.), 0.2-1.2 (D.), 3.0 (G.). Water absorption: 0.2-0.4% by weight and 0.5-1.1% by volume (B.). The mass of 1 m 3 of dry basalt is about 3 tons. Compressive strength in kg / cm 2: 2000-3500 (B.), 1800-2700 (D.), 1000-1900 (G.). If the compressive strength of dry basalt is more than 3000, then wet basalt is more than 2500, and at a frost of 25 ° it is more than 2300. Wear strength ("hardness" calculated by the formula: p = 20-w / 3, where w is the mass, lost under normalized conditions at 1000 revolutions of the abrasive disk) is characterized by the numbers 18-19 (B., D., G.). Impact strength ("compactness") when testing standardized samples: 6-30 (B., D.) and 8-22 (G.). Basalt is superior in hardness to steel. Young's modulus in (D cm -2) x10 -11 is 11 (G.) and 9.5 (D.). The volumetric compression ratio per 1 kg at a pressure of 2000 kg / cm 2 is 0.0000018 (B.) and 0.0000012 (D.), and at a pressure of 10000 kg / cm 2 is 0.0000015 (B.) and 0.0000012 (D.). The beginning of melting of normal olivine basalt is at a temperature of about 1150 °, and the liquid-melting state begins at a temperature of about 1200 °. The molten rock ceases to flow when cooled to 1050 °. More acidic rocks have a higher melting point, and it rises with silicic acid content. In particular, the basalt of the Adjaris-Tskhal deposit (dacitobasalt - according to Abikh or trachyandesite - according to new definitions) softens at 1180 °, has the consistency of thick honey at 1260 ° and completely liquefies at 1315 ° (the author's experiments in the materials science department of the SEEI). The specific heat of Syracuse basalt for different temperatures is shown in the following table:

Heat of crystallization of basalt during the transition from amorphous to crystalline state 130 Cal. During crystallization, the volume decreases by 12% compared to the volume of basalt at a temperature of 1150 °. The specific thermal conductivity of basalt in gram-calories is about 0.004. Basalt thermal expansion coefficient: 0.0000063 (at 20-100 °), 0.000009 (at 100-200 °) and 0.000012 (at 200-300 °).

Chemically, basalts are resistant rocks: atmospheric agents, in Gary's experiments, weathered from 1.5 to 0.8 mg / cm 2 of basalt in 18 months, while gray limestone lost 22.7 mg / cm 2 under the same conditions. The course of the process of weathering of basalt and diabase is presented by a comparative diagram (Fig. 2).

The number on the upper horizontal line shows the number of grams of weathered rock that must be taken so that it contains the component corresponding to the designation of the horizontal line in question, the same as this part is contained in 100 g of fresh rock. That. all points to the right of the vertical 100 denote depletion of the corresponding part, and those to the left denote enrichment. Consequently, during weathering, basalt is enriched in silica and alumina and becomes poorer in alkalis, alkaline earths and iron in all forms, while diabase is enriched in iron oxide and sodium. This circumstance apparently speaks against diabase as an insulating material.

3. Grounds for processing basalt... The properties of natural basalt make it an excellent building material, more durable than granite. Basalt has been used for a long time. However, the extreme difficulty in processing basalt and dividing it into relatively narrow prisms forced to come up with a special way of giving it geometric shapes.

It was natural to think about fusing this rock, since it itself is of fiery origin. But it is not enough to melt the basalt: upon rapid cooling, castings from it give a glassy mass, similar to natural hyalobasalts, fragile and technically inapplicable (Figs. 3 and 4).

The main task of basalt production is to restore the fine-grained content of remelted basalt, the so-called regeneration (Fig. 5).

The idea of ​​the possibility of melting and restoring rocks to their original form arose in the 18th century. The Scotsman James Goll already in 1801 achieved the remelting of basalt and, in particular, established that basalt and lavas, being melted and rapidly cooled, give glass, while when slowly cooling them, a stony mass is obtained, with traces of a crystalline structure; this is the basic principle of fiery lava processing. Especially remarkable are the experiences of the Scotsman Gregory Watt, who expanded the scale of the smelting. The melting of a lump of basalt more than 3 tons lasted 6 hours, and cooling under the cover of slowly burning coal took 8 days. Watt described the products of this slow cooling: black glass on the surface; as you go deeper into the solidified mass, grayish balls appear, grouping into bundles; then the structure becomes radiant; even deeper, the substance has a stony and then granular character, and, finally, the mass is penetrated by crystal plates. That. the possibility of melting and regenerating igneous rocks was found out. But due to the lack of a sufficiently large demand for remelted basalt for industry, the described experiments were forgotten. In 1806 Dobre and then in 1878 F. Fouquet and Michel Levy returned to the process of smelting and regeneration. They managed to reproduce almost all rocks of fiery origin and found out that this does not require any extreme temperatures or mysterious agents, but the whole point is to establish the proper melting and annealing regime. After cooling, the molten silicate turns into glass, the melting point of which is lower than the melting point of the original mineral. To restore the latter, it is necessary to anneal the vitreous mass at a temperature higher than the melting point of the vitreous body, but below the melting point of the crystalline mineral. The temperature range of these melting points is the region in which the regeneration of silicate or aluminosilicate is possible; this interval m. b. rather insignificant. When it is not about a single mineral, but about a set of 5-6 minerals that make up a crystalline rock, then the annealing mode would have to be set with a number of stages, and each mineral would have its own stop in the cooling process. However, in practice, these steps are so close to each other that you can limit yourself to two stops. In relation to basalt, the first annealing, with a red-white glow, gives crystallization of iron oxide and peridot, and the second, with a cherry red, crystallization of other minerals of the rock.

The first experiments with industrial smelting of basalt were undertaken in 1909 by Ribb, and various applications for fused basalt were found by engineer L. Dren. In 1913, for the industrial implementation of smelting processes, the Compagnie generate du Basalte was formed in Paris, and in Germany - Der Schmelzbasalt A.-G., in Linz on the Rhine; then both societies merged under the common name "Schmelzbasalt A.-G.", or "Le Basalte Fondu". Currently in France there are two factories producing hl. arr. electrical and construction products, and in Germany there is one serving the chemical industry.

4. Production of fused basalt... Breaking. The occurrence of basalt is different, and therefore its breaking is not always uniform. Slab-like basalt of covers or rocks is mined by demolition work. Columnar basalt prisms can be detached by means of wedges and levers. Development is carried out in tiers, removing successive layers in rows of natural layering.

Splitting up . Broken basalt is stored outdoors. For smelting, it is crushed in Black or Gets crushers. Then the pieces are sorted by size, and the fines go to the concrete mass.

Remelting. The crushed basalt is fed to smelting forges, which use various heating methods. The most suitable furnaces are electric, gas (gas generator or with lighting gas) and furnaces with oil nozzles. The electric smelting installation consists of a stationary electrode furnace and a mobile receiver on wheels, which serves to transport molten basalt through the casting shop; this receiver is also a small electrode furnace. Both types of ovens are powered by a two-phase current. The bottom of the furnace is made of refractory material and has a nozzle on the side for discharging the molten mass, from the receiver it descends into molds or molds for casting by simply tilting the receiver. In other furnaces, the throat is made inclined, so that the loading of the hearth and the descent of the molten mass are carried out in a continuous process. The productivity of the described furnaces is from 3 to 50 tons per day. The Parisian plant - large-scale handicraft type - has 4 ovens with a capacity of 80 kg each, operating continuously and heated by city gas; melting is carried out at 1350 °. Another French plant, at Puy, is powered by electricity. Continuous production capacity - 8 tons per day.

Casting. The molten basalt is poured into molds or molds directly from the furnaces or taken to the casting workshops. For casting, either sand trusses or steel molds are used. The first ones are much cheaper, but they are not applicable in all cases, since the products come out of them dull and rough. Steel molds give products a shiny surface, but are relatively expensive. With careful casting, the casting is clean; otherwise, streaks and irregularities are visible, which in many cases do not prevent, however, the use of the product.

Heat treatment... Almost immediately after casting, the products, still cherry red, are removed from the molds and transferred to annealing hearth furnaces, similar to conventional hardening furnaces. Depending on their purpose and size, the products are kept in the oven from several hours to several days. The initial annealing temperature is about 700 °. The oven is smeared over and slowly cooled; languishing in the oven lasts, depending on the size of the products and their required qualities, from several hours to 10-14 days. There are up to 35 such ovens at the Paris plant.

Finishing. After cooling, the products are ready for use. To give them the proper look, they are cleaned off the plaque with steel brushes. If greater accuracy of planar edges is required, then finishing is performed on circles with a basalt base.

production cost... The production of fused basalt does not require highly skilled labor or expensive equipment. The main production costs in our conditions are for the delivery of material, if it is brought from the Caucasus, and for energy. When working with gas, about 900 Cal is required per 1 kg of finished basalt products, that is, about 1/4 - 1/3 m 3 of gas; when working with electric energy, about 1 kWh is consumed per 1 kg of products. That. the cost of basalt products, for example, insulators, is much lower than porcelain. In France, the selling price of basalt insulators is 10-15% less than porcelain insulators, and for larger ones - 25-30%. The larger the items, the greater the price discrepancy between basalt and porcelain. However, there is reason to consider the above discrepancies in selling prices significantly understated due to the increase in the profit of basalt production as a new business.

Fused basalt production in the USSR... With its enormous technical and economic advantages and in some cases, such as in the electrification of railways, being almost irreplaceable, the basalt industry has attracted the attention of the technical and industrial circles. Experiments with melting basalt and other rocks undertaken on behalf of Glavelektro VSNKh in the Department of Materials Science of the SEEI and then at GET, experiments on melting diabase in the Mining and Metallurgical Laboratory and the interest of the Supreme Economic Council of Georgia and Armenia in this industry can be considered harbingers of the rapid development of the basalt business. From an economic point of view, d. B. a very favorable natural combination of favorable factors was noted: the possibility of basalt mining very often geographically coincides with the availability of hydroelectric energy sources for its processing, i.e. acid-resistant basalt equipment. The indicated coincidence, due to the profitability of small basalt factories and the comparative high cost of transport, makes it possible to foresee in the future a network of small basalt factories throughout the country.

5. Properties of recycled basalt... Remelted and reclaimed basalt generally has the properties of natural, but in an improved form (see Fig. 3 and 5).

Mechanical properties: a) compressive strength - about 3000 kg / cm 2; b) The wear resistance tested with the sand-powdered Derry mill was 0.9 mm on average after 1000 revolutions; c) having a high viscosity, basalt does not break easily, and basalt insulators and other products can practically be considered unbreakable. Compared to porcelain, basalt is 2-4 times less fragile; different values ​​of this quantity depend on the annealing mode; the presence of impurities brittleness m. b. highly increased; d) tensile strength was tested on basalt supports for the third bus of electrical railways. and for comparison, the same sandstone supports were tested; rupture of basalt products was observed at 3700-4700 kg, and rupture of the same products from sandstone - at 1200 kg.

Thermal properties: a) remelted basalt resists temperature changes, even sharp; a plate of basalt 8 mm thick, immersed alternately in boiling water and in cold water, did not show any signs of cracking; insulators exposed to the sun and then exposed to a thunderstorm, as well as insulators tested according to the rules of the French Union of Electrical Syndicates (sudden transfer from water at 65 ° to water at 14 °) showed no change in electrical properties; the upper limit of the thermal interval can be further increased; b) at the moment of solidification, the basalt allows for stamping or other introduction of iron parts of any volume into it and adheres firmly to them without requiring cementation; c) basalt can withstand significant heat without showing ruptures, cracks, "fatigue" or "aging"; d) basalt can serve as a thermal insulator due to its low thermal conductivity.

Hygroscopicity... Being quite compact and covered with autogenous glaze, basalt is completely waterproof and non-hygroscopic.

Electrical properties: a) basalt has a significant electrical strength: for bridge basalt, it turned out to be about 32 kV / cm with a plate thickness of 18 mm, and for special electrical basalt, both heat treated and vitrified, it was from 57 to 62 kV / cm at the same thickness; b) when a breakdown occurs and a powerful arc is formed, the basalt insulator is still not damaged by this, because after the arc stops, the breakdown site floats, and the insulator heals without a trace; c) basalt insulators, when processed by themselves, are covered with glass-like basalt glaze 1.5-2 mm thick, gradually turning inward to granular basalt; This glaze is an excellent barrier against surface electrical leakage and protects insulators and other products from hygroscopicity and atmospheric agents; having a composition identical to the composition of the insulator itself, the glaze adheres to it like a homogeneous body and therefore is not in danger of cracking or peeling off. In addition, in case of violent damage to this glaze, a substance of the same composition is exposed, so that the specified damage is not fatal for the insulator.

Chemical properties... Chemically, basalt products, according to French sources, are very stable; in table. 1 shows data on the effect of various reagents on recycled basalt.

Further test data are given in table. 2.

Appearance . Remelted, but unannealed basalt resembles glass: it has a shiny fracture, brown-black color, and is fragile. After annealing, the remelted basalt gets black or dark color, matte fine-grained fracture and the toughness of natural rock. The external appearance of the products depends on the material of the mold and the mold (see item 4).

So, in terms of mechanical strength, thermal and chemical resistance, high and peculiar electrical properties, cheapness and relatively easy workability, processed basalt should be recognized as one of the most remarkable materials in electrical engineering.

6. The use of recycled basalt... The basalt industry is still too young to foresee all the uses of the new material at present. So far, the following have been outlined: a) in networks of high currents of high and low voltage - linear insulators in the open air (Fig. 6),

support insulators, insulators of the third bus of electrical w. etc. and subways (Fig. 7), output insulators at high voltage;

b) in low-current networks and in radio communications - telegraph and telephone insulators, pull-off insulators and other insulating parts for antennas; c) in the electrochemical industry - insulator stands for batteries, dishes, baths, etc.; d) in the general chemical industry - acid-resistant equipment, including all kinds of dishes, baths, taps, propellers, etc., equipment for temperatures up to 1000 °; e) in construction - insulating bridges (Fig. 8), bridge, staircase, wall and floor cladding, especially when there is acid fumes, etc.

Line insulators... In view of the exceptional interest represented by basalt in electrical engineering, we present the test data in the Paris Central Electric Laboratory of ten insulators with iron pins embedded in them, and five of them were previously subjected to a thermal test (see clause 5). In the dry test, the first sparks sliding over the insulator appeared at 32.5-38 kV, the arc was formed at 35-43 kV, the breakdown of the skirt was obtained at 40 kV, and the neck breakdown at 37.5-39.5 kV. A wet test under artificial rain produced an arc at 18-20 kV, followed after 30 seconds. the insulator was breaking through. A test under oil established a breakdown voltage at 35-58 kV. Testing of pull-off insulators with alternating voltage, which was raised before breakdown and then, immediately after breakdown, began to rise again until a new breakdown, and so 4 times, gave the results presented in table. 3.

Telegraph insulators... By testing high current basalt insulators, similar to telegraph ones, produced at the Moscow Scientific Testing Telegraph Station, the surface electrical resistance of basalt insulators is significantly higher than that of the corresponding porcelain insulators; but when tested in the rain, the resistance of basalt recovered somewhat more slowly than that of porcelain. This probably depended on the rough surface of the high current insulators tested, for which the telegraph requirements were not taken into account.

7. Other uses of basalt... In addition to the use of natural basalt as a building material and crushed stone, and the use of thermally processed basalt in various industries, basalt and related rocks are also used as an integral part in ceramic and glass production. So, Borjomi andesite has been used for several years for making glass for bottles under Borjomi mineral water, giving it strength and dark color. The English Wedgwood Porcelain Factory has long produced earthenware with a black unglazed by weight and easily polished shard, the so-called. "Basalt" or "Egyptian" - the mass for it contains basalt.

Basalt (from the Greek βασικός - basic) is an effusive igneous rock of basic composition. The basalt layer of rocks is isolated in the earth's crust, and extends both to the continental and oceanic crust. Basalt is an effusive analogue of gabbro.

Dark color: black, dark gray. Structure: dense, fine-grained. The texture is porous, almond-shaped or massive. The fracture is uneven. Rough to the touch. Specific gravity 2.6-3.11 g / cm 3. Hardness on the Mohs scale from 5 to 7. Melting point 1100 - 1450 ° C. The compressive strength of the rock reaches 400 MPa. The form of bedding of the rock is most often: streams, covers, domes, dikes. Separation forms are columnar or limestone.

Features... Basalt is characterized by a dense, fine-grained structure, uneven fracture, dark (mostly black) color, high density.

Basalt composition

Mineralogical composition of basalt. Composition is difficult to determine without a microscope. A composition similar to that of gabbro is observed under a microscope. Basalt is composed of olivine, augite, and feldspar (plagioclase).

Chemical composition... SiO 2 45-52%, Al 2 O 3 15-18%, Fe 3 O 4 8-15%, CaO 6-12%, MgO 5-7%, etc.

Varieties and photos of basalt

  1. Trap- basalt with seam separation.
  2. Dolerite- coarse-grained basalt.


Origin of basalts

Basalt formation occurs during the outpouring and solidification of basic lava (SiO 2 content 45-52%), both on the surface of continents and in the depths of the oceans. Basalts are the most common igneous rock on the planet, the bulk of which is formed precisely in the oceans, in the mid-ocean ridges, forming the base of oceanic tectonic plates (oceanic crust).

Basalts practically do not undergo any secondary processes after formation, being a typical kainotypic volcanic rock. During hydrothermal processes, olivine is replaced by serpentine, and plagioclase by sericite; the rock is chloritized and acquires a greenish tint. Such changes are typical mainly for basalts formed in mid-oceanic ridges.

As a result of metamorphism, depending on conditions, basalts transform into amphibolites, green and blue shales.

Basalt application

Basalt is used as a building, facing, acid-resistant material, as well as a raw material for stone casting. The addition of basalt fiber (shavings) increases the impact-strength characteristics of concrete products by 5 times.

The rock is used for the manufacture of a widely used heat-insulating material - stone wool or, as it is also called, basalt fiber. For the manufacture of basalt wool, basalt crushed stone is returned to the state of liquid lava - it is melted, and with the help of a simple mechanism, liquid basalt is converted into thin threads, which compose stone wool.

Basalt deposits

Basalts prevail in distribution among all volcanic rocks. In Russia, basalt is found in Kamchatka, in Altai (Sinyukhinskoe), in Transbaikalia (Angara-Ilimskoe, Zandinskoe), Khabarovsk Krai (Kholdaminskoe, Marusinskoe).

There are large deposits in Armenia (Jermuk, Moz and Kogbek), Ukraine (Ivanchinskoe, Ivano-Dolinskoe, Berestovetskoe), Ethiopia, India (Jakan plateau).