Mineral composition of basalt. Basalt stone description

Magnetite, etc.

Basalt- the main effusive rock of the normal series, the most widespread of all kainotypic rocks. The main minerals of phenocrysts are clinopyroxene and calcium plagioclase (N 30–90), sometimes olivine, orthopyroxene; the bulk is composed of the same minerals (without olivine) and magnetite in glass (or without it).

History of the name

This mineral became basalt from the Latin basaltes, basanites, from the Greek. basanos - touchstone; according to another version, they became basalts from the Ethiopians. basal is an iron-bearing stone.

Classifications

Varieties can be distinguished according to the peculiarities of the mineral composition (apatite, graphite, dialagic, magnetite, etc.), the composition of minerals (anorthite, labradorite, etc.), the peculiarities of the structure and (or) texture, chemical composition (ferruginous, ferrobasalt, calcareous, alkaline - calcareous, etc.).

Petrochemical classification

Yoder and Tilley (1962) proposed to use nepheline-olivine-diopside-quartz tetrahedron for classification. The activity of silica in the melt is controlled mainly by reactions of the type:
2 (Mg, Fe) SiO3 -> (Mg, Fe) 2SiO4 + SiO2 (orthopyroxene = olivine + silica)
NaAlSi3O8-> NaAlSiO4 + SiO2 (albite = nepheline + silica)

These reactions can be divided into 3 groups:

• quartz-regulatory (containing excess silica)
• nepheline-normative (lack of silica)
• hypersthene-normative (in the absence of normative quartz or nepheline)

Belonging to these groups is determined by the chemical composition of the rock, by the presence of the corresponding normative minerals in the results of petrochemical recalculation according to the CIPW method.

Geodynamic classification

According to the geodynamic setting, the main types are distinguished:

• Mid-ocean ridges BSOH or MORB
• Active Continental Margins and Island Arcs (IAB)
• Intraplate, which can be subdivided into continental and oceanic (OIB).

Composition and structure

Usually these are dark gray, black or greenish-black rocks with a glassy, ​​cryptocrystalline aphyric or porphyry structure. In the porphyry varieties, against the background of the total cryptocrystalline mass, small phenocrysts of greenish-yellow isometric crystals of olivine, light plagioclase, or black pyroxene prisms are clearly visible. The size of phenocrysts can reach several centimeters in length and make up to 20-25% of the mass of the rock. The texture in basalts can be dense, massive, porous, and amygdaloid. Tonsils are usually filled with quartz, chalcedony, calcite, chlorite and other secondary minerals - such basalt are called Mandelstein. The bulk is often not crystallized. Aphyric (no porphyry disseminated) varieties are frequent.

The basalt flows are characterized by columnar jointing. It occurs due to uneven cooling of the rock. Marine basalts are often cushioned. It is formed as a result of the rapid cooling of the surface of the lava flow with water. The incoming magma lifts the formed carapace, flows out from under it and forms the next cushion.

Prevalence

Basalt is the most widespread effusive rock on Earth and on other planets. The bulk in basalt forms in mid-ocean ridges and forms the oceanic crust. In addition, basalts are typical for environments of active continental margins, rifting, and intraplate magmatism.

During the crystallization of basaltic magma at depth, strongly defended, layered intrusions are usually formed (such as the Norilsk, Bushveld and many others). They are composed of various rocks, the crystallization sequence of which is determined by the dynamics of magma crystallization. First, the highest-temperature minerals crystallize from the melt, but they are deposited on the bottom of the magma chamber. in this case, the melt is enriched in some components and depleted in others. As the temperature decreases, the crystallizing minerals change.

In the layered massifs, there are deposits of copper-nickel ores, chromites and platinoids.

Origin

Basalts are formed during partial melting of typical mantle rocks - lherzolites, harzburgites, wehrlites, etc. The composition of the smelt is determined by the chemical and mineral composition of the protolith, the physicochemical conditions of melting, the degree of melting and the mechanisms of melting.

Analogs

• The hypabytic analogue, dolerite, has a characteristic dolerite structure.
• Intrusive analogs of basalt are gabbro, gabbronorite, norite, troctolite.
• Paleotypic analogue of basalt - diabase

Changes

Basalts are very easily altered by hydrothermal processes. In this case, plagioclase is replaced by sericite, olivine by serpentine, the bulk is chloritized and, as a result, the rock acquires a greenish or bluish color. Basalts, pouring out at the bottom of the seas, change especially intensively. They actively interact with water, while many components are carried out and settle out of them. This process is of great importance for the geochemical balance of some elements. So most of the manganese enters the ocean in this way. Interaction with water dramatically changes the composition of marine basalt. This influence can be estimated and used to reconstruct the conditions of ancient oceans from basalts.

Metamorphism

During metamorphism in basalt, depending on conditions, it turns into green shales, amphibolites and other metamorphic rocks. During the metamorphism of basalts at significant pressures, they turn into blue shales, and at high temperatures and pressures into eclogites consisting of pyrope and sodium clinopyroxene - omphacite.
Metamorphic rocks with a composition close to basalts are called metabasites.

Basalt application

Basalt is used as a raw material for crushed stone, for the production of basalt fiber (for the production of heat and sound insulation materials), stone casting and acid-resistant powder, and also as a filler for concrete. Basalt is highly resistant to weathering and therefore is often used for exterior decoration of buildings and for making sculptures for outdoor use.

Rock Properties

• Rock type: Igneous rock
• Colour: dark to black
• Color 2: Black gray
• Texture 2: porphyry
• Origin of name: from Latin basaltes, basanites, from Greek. basanos - touchstone; according to another version, from the Ethiopian. basal - iron-bearing stone
• Structure: porphyry
• Texture: amygdala

Rock Photos

Deposits Rocks Basalt

• Sinarskoe
• Evenk Autonomous Okrug
• Russia
• lake

Natural stones and rocks have long gone out of the category of only finishing or ballast materials. Thanks to new technologies and chemical processes, classic stones such as basalt or granite are deeply processed to obtain artificial stone structures that have the resistance and hardness of the rock.

What is basalt mineral

From the point of view of chemistry and mineralogy, the natural material basalt is a complex structure in which crystalline formations and fine-grained inclusions of magnetite, complex silicates and metal oxides are intertwined. Basalt rock is of magmatic origin, so its structure is more reminiscent of a complex mixture of amorphous volcanic glass, micron crystals of feldspar, quartz, carbonates, sulfide ores.

Basalt stone is easy to distinguish from other volcanic rocks, primarily due to its black, smoky black, greenish color. This stone has found wide use in construction and the production of special materials for the chemical industry due to a number of specific properties:

• The material is very heavy and hard, the density of basalt rock can vary from 2.5 to 3 kg per dm 3, high hardness provides good resistance to abrasion, including under the action of abrasives and water flows.
• The high melting point makes it possible, in some cases, to use the rocks that are included in the basalt to obtain fire-resistant and refractory materials.

Important ! The simplest use is to cut basalt massifs into facing stones and slabs. Due to the specific natural color of the rock, finishing in black or black-green is widely used for cladding the walls of basements and porches.

The main directions of use of basalt

The most inefficient way is to use basalt as ballast, crushed stone for road construction, filler for concrete castings, and filling in foundations. In some deposits, basalt stone has a relatively high coefficient of water absorption, due to which screenings from such a stone can be used for the manufacture of exceptionally strong concrete foundations, walls, arches, bearing columns.

Products of deep processing of basalt

The most famous basalt materials obtained by rock remelting are heat insulators, various grades of fiber material, felt. Basalt mineral fibers are highly resistant to high temperatures and open flames. For example, a heat-insulating mat made of basalt fiber with a thickness of only 5 cm can withstand direct heating of a gas burner without destruction and burnout, while the temperature on the reverse side of the heat insulator does not rise above 50 ° C.

In addition, basalt fiber does not give sharp chips, like fiberglass and glass wool, so it is safer for human skin, and any dust from basalt insulation can be easily removed with water. Nevertheless, when handling any basalt heat insulators, it is necessary to use respirators, safety glasses. Fiber material several microns thick produces a large amount of dust, which is highly irritating. After finishing work, you must thoroughly wash your face, hands and other exposed areas of the body in order to get rid of basalt dust, which can easily penetrate even through protective gloves.

Basalt felt is considered the most suitable and durable material for arranging the protection and thermal insulation of chimneys, chimneys, fireplace inserts and stoves. Previously, asbestos fiber was used for such purposes, which was abandoned in favor of basalt. Due to the high melting point of basalt, the production of fiber requires significant costs, therefore, thermal insulation based on it stands out at a relatively high price.

Remelting of basalt rock gives not only fiber for the production of heat and thermal insulation, a similar method of high-temperature melt casting produces:

1. Shaped parts and elements, tiles, floor covering of non-standard shapes, intended for installation in places with high traffic intensity. Due to their high hardness and wear resistance, the service life of such coatings significantly exceeds the wear parameters of clinker tiles, various types of sintered materials from ceramics, dolomites, marble, calcite and other types of decorative stone and rocks.
2. The high density of basalt stone makes it possible to cast from the melt a specific type of product for high voltage power grids. Basalt rock insulators have significantly higher dielectric characteristics than ceramic or glass insulators. But not all types of basalt stone have similar properties; a rock with an exceptionally high density, up to 3 tons per cubic meter, is suitable as a raw material. Such rock has to be mined from depths of at least 70 meters of seam in the mine.
3. In addition to mechanical properties, products from fused basalt are highly resistant to alkalis and acids at high temperatures, therefore, shaped castings are often made from basalt for the construction of various kinds of apparatus, product pipelines, and containers in the chemical industry.

Finishing decorative forms of basalt

In addition to industrial use, basalt is increasingly used as a decorative stone because of its black with shades of gray, smoky, sometimes greenish color. The most famous type of basalt decor is considered to be Italian-made facing tiles. Basalt tiles with a specific texture with a beautiful pattern can be compared to a marble or marbled limestone finish.

Recently, finishing materials from natural basalt stone with a specific smoky shade of the surface have appeared on the market. Due to its characteristic texture, natural stone from China is in increasing demand in the decoration of stairs and the creation of monuments, sculptures, and facing of fountains. Cheaper varieties of basalt stone are used for the construction of decorative fences, columns, entrances, verandas. More and more often, basalt stone is used as a material for the construction of monuments, steles, elements of gravestones and crypts.

High abrasion resistance makes it possible to use basalt in the form of paving stones for paving pedestrian areas and roadways. Moreover, the service life of such a coating can reach tens of years. In addition to paving stones, cast slabs are used, which in some cases successfully replace the finishing of stairs and steps made of porcelain stoneware, natural granite, gabbro and more expensive finishing materials.

Conclusion

Despite all the advantages of basalt, it is not recommended to use it for interior decoration, since this rock, like other heavy rocks of magmatic origin, can have an increased background radiation. Therefore, a careful check and control of the radioactivity level of this finishing material is required before using it.

BASALT (Latin basaltes, basanites, from the 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, textures - 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 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 raw materials 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 foundry materials have great chemical and 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).

The word "basalt" is of Ethiopian origin. It was formed from the word "basal", which literally means "boiled". This is the name given to the stone because it is formed in the incandescent vents of volcanoes, in which temperatures reach several thousand degrees.

The stone is easily recognizable by its appearance. It has a dark, black, gray-black, ash color. The mineral is very hard and has a high density. Basalt consists of calcium feldspar and its varieties. There are also olivine impurities.

Basalt is found in nature mainly in the form of interstratal bodies or in the form of lava flows, which appear as a result of eruption through the main volcanic vent or through the cracks of the volcano. In theory, two types of basalts are distinguished: those that contain olivine and those that do not (tholeiitic basalts).

In the latter, quartz elements are also often present. Basalts with olivine are most often found on islands, especially in those located in the volcanic belt of the Pacific Ocean. Tolein rocks create the so-called tramp formations of the continents.

Huge deposits of basalt were found in the form of lava flows in India (in its western part, on the Deccan plateau), in the USA (Washington states, Oregon and Idaho on the Columbia plateau, in the Hawaiian Islands). The rocks at the Etna and Vesuvius volcanoes in Italy are also rich in this mineral. On the territory of the former USSR, the mineral was actively mined and extracted from the lava flows of volcanoes on the Kuril Islands and Kamchatka. Basalts can also be found on the territory of Ukraine and in Altai, but these deposits are underdeveloped. In Europe, the most famous are basalts, which are mined in Iceland, Scotland and Ireland.

The healing properties of basalt

At the moment, the medicinal properties of basalt are mainly used in stone therapy. This method of treatment has been known since ancient times, we began to practice it relatively recently, having adopted the experience of our eastern colleagues.

Stone therapy is able to strengthen the body's immune system. This technique is based on the use of stones, the main of which is basalt. Doctors recommend using dark gray and black breeds for this procedure. It is best to use basalts containing olein.

It is believed that basalt combines all four elements: fire, earth, air and water. The stone keeps heat in itself for a long time, therefore its effect on the body is maximal in thermal terms.

The magical properties of basalt

The magical properties of basalt are still insufficiently studied, therefore, a uniform practice of its use has not yet been developed. It is believed that basalt carries male energy, Yang energy. Therefore, it is usually used in combination with other minerals.

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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, which is why 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. 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.