melting point of granite. Granite - characteristics and properties of the rock Physical properties of granite

GRANITE is a crystalline rock composed of feldspar, mica and quartz.

Granites are a widespread rock found on all continents of our planet. Sometimes they come to the surface in areas composed of ancient rocks, where, as a result of erosion processes, the overlying deposits were destroyed.

However, in most cases, the solidified magma from which granites were formed does not reach the surface of the earth's crust and solidifies (crystallizes) at different depths, forming bodies of unequal shapes and sizes. Granite, as a rule, has a granular structure: from fine to coarse-grained

Granite is a complex natural natural stone. Mainly formed from feldspars, mica and quartz

TITLE

Granite (from lat. granum - grain)

COLOR

Depending on the proportional combination of minerals, it acquires various colors. It has a rich color range: from black - to the traditional red-burgundy with black - to white with gray.

By the way, it is feldspar and quartz that create the “spotted” effect.

Granite is coarse-grained, medium-grained and fine-grained. This amazing stone has a rich color range, from the traditional red-burgundy version with black flecks to white with gray blotches (and vice versa).

The most common granites are gray (“Siberian”, Gray Quenna) and black (Absolute Black, Nero Africa), but there are also rocks of pink-red (Rosso Marina), white (“Mansurovsky”), yellow (“Zhiltau”) and green ( Forest Green) tones.

PLACE OF BIRTH

Granites are a widespread rock found on all continents of our planet.

In the United States, granites are distributed along the coast of the Atlantic Ocean (from Maine in the north to Georgia in the south), they form large massifs in the north of the country, in the central part of the Ozark plateau, in the Black Hills and the Front Range of the Rocky Mountains.

In Russia, about 50 deposits of granite suitable for use as piece stone, as well as rubble and crushed stone, are known - on the Karelian Isthmus, in the Onezhye and Ladoga Regions, the Arkhangelsk and Voronezh Regions, in the Urals, in Primorye and Khabarovsk Territory, Eastern Transbaikalia.

A large granite deposit is located in Ukraine. Across the entire territory of the country, from the northwest to the southeast, the Ukrainian crystalline shield stretches. The width of its part, directly coming to the surface, is 200 km, and the length is about 1000 km. It is on this strip that the main deposits of decorative stone are concentrated.

QUALITIES

1.Durability. The best varieties of fine-grained granite begin to show the first signs of destruction after more than 500 years, so it is often called the "eternal" stone;

2.Strength. Granite is highly resistant to friction, compression and abrasion. It is a very dense (2.6-2.7 t / m³) and durable stone (its compressive strength is 90-250 MPa - twice that of marble);

3.Resistant to weathering and acids. Granite is an ideal stone for exterior decoration of buildings.

4.Waterproof. Granite practically does not absorb moisture (water absorption coefficient - 0.05–0.17%). That is why granite is perfect for facing embankments.

5.Environmental friendliness. Contrary to prevailing prejudices, the natural radiation level of most granites corresponds to the 1st class - i.e. they are radiation safe and suitable for all types of construction without restrictions;

6. Wealth of textures. Unpolished, rough stone that absorbs light; polished to a mirror shine, showing the world a unique light play of mica inclusions - the decorative possibilities of granite are able to satisfy even the most complex design ideas;

7. Compatibility with other materials. Granite goes well with wood, metal, ceramics and other materials used in modern construction. It will "fit" into any interior - from classic to ultra-modern;

8. Rich color palette. The most common is gray granite, but there are also red, pink, orange, bluish-gray, bluish-green.

APPLICATION

In modern construction, granite is used so widely that, without exaggeration, it can be called a universal material.

Floors, stairs. Granite is a material with a very low level of abrasion. Even if the stairs in your private apartment a year will pass 1 million people, they can erase its steps by no more than 0.12 mm;

Various interior details. Window sills, cornices, skirting boards, railings, furniture tops, coffee tables, bar counters, balusters, columns - the high strength of granite will allow these items to remain intact for many years, to avoid mechanical damage due to temperature and humidity;

Facade and interior decoration. Granite is a very ergonomic material that can provide you with a comfortable stay in a building;

Elements of landscape design. Alpine hills, rockeries, Japanese gardens, decorative ponds - made of granite, these fashionable compositions will give your garden naturalness and originality.

Borders, steps, paving stones for pavements. Granite is successfully used in places where more "endurance" is needed. It is resistant to mechanical stress, chemical pollution and temperature changes - it does not change its properties during hundreds of freezing and thawing cycles.

Embankment lining. Granite practically does not absorb moisture - accordingly, when the temperature drops, additional internal pressure from frozen water does not form in the pores of the stone, which can lead to the formation of cracks and destruction of the rock.

Granite paving stone. The use of granite paving stones dates back thousands of years. The famous ancient Roman cobbled roads can still be walked today; paved streets, you will find in the old part of any of the European capitals; in modern cities, stone roads are gradually replacing asphalt and concrete.

MAGICAL AND HEALING PROPERTIES

Ever since primitive times, man has been accustomed to trust the stone. This natural, living, "feeling" material will relieve psychological stress, bring coziness, tranquility and comfort to your home.

Have you ever thought about the origin of the expression "nibble on the granite of science"? Why, speaking of diligent and capable students, do we remember exactly granite, and not any other stone? It turns out there is an explanation for this. According to some observations, granite has the ability to stimulate human mental activity, helping to achieve success in scientific research.

Granite is referred to by some geologists as the "marker of the Earth". On other planets of the solar system, similar rocks have not been found. This stone holds a lot of mysteries, and not all answers to them have been found. And the point here is not so much in the chemical composition of granite, but in its structure and occurrence features. This breed is widely represented in the continental crust, but it is not found on seabed. To date, many varieties of this stone have been studied, and it has been used since ancient times.

Mineralogical composition

Sometimes people have confusion in concepts, and they cannot understand what granite is - is it a mineral or rock. Certainly the second. Many paid attention to its granular structure, and definitely - it does not consist of one substance. Even from school lessons in natural history, many remember what minerals are included in granite. This is first of all:

Gneiss also consists of a similar set - what is obtained from granite by metamorphism.

In gneiss and granite, the formulas of the mineral composition are almost identical, only the structure differs.

feldspars

These are silicate crystalline compounds, which can be contained in the earth's crust up to 50%, and for the most part - in the composition of other rocks. They do not have a single formula, and they are divided into categories based on the presence of certain metal atoms in the crystal lattice. On this basis, plagioclases, potassium and potassium-barium feldspars are distinguished. . The plagioclase group includes:

In igneous rocks, plagioclases are the first to form crystal lattices, and they often make up most of the rock. Potassium feldspars are less diverse in chemical composition, they have the same formula - KAlSi₃O₈. The diversity lies in the structure of the crystal lattice, and it in various modifications gives the following minerals:

  1. orthoclase;
  2. adularia (moonstone);
  3. microcline;
  4. sanidine.

Potassium feldspars are more stable than plagioclases, but, like them, they become clay under the influence of erosion. When some potassium atoms are replaced by barium, potassium-barium spars are obtained, but this is a rare occurrence.

In the composition of granite, these minerals make up from 60 to 65%, and the color of this rock depends on them. Plagioclases give the stone a gray color, potassium compounds - pink. Yellow, green and blue colors give the stone both foreign inclusions and metal cations in spars - sodium, potassium, calcium, magnesium and other metals are interchangeable in them.

Quartz and its modifications

With such a simple formula, this compound has four types of polymorphic modifications:

  1. pseudocubic (cristobalite);
  2. hexagonal (tridymite);
  3. monoclinic syngony (coesite);
  4. dense octahedral (stishovite).

Modifications are given in order of increasing pressure required for their formation. Naturally, the first two minerals are more common in nature. The last of them - stishovite - was obtained in the laboratory and is sometimes found in places where meteorites fell. Large crystalline bodies in nature can be found infrequently, but various bulk conglomerates are very diverse. So, quartz makes up the bulk of such minerals as amethyst, agate, chalcedony, onyx, cat's eye, citrine, heliotrope and others. But in the form of inclusions, it occurs much more often.

Granite includes up to 35% of this mineral. Among all its components, quartz is the most tenacious: as the rock breaks down, feldspar turns into clay, and sand remains.

Role of mica in granite

This mineral is up to 10% in the composition of granite, its arrangement in the massif is uniform. It is mica that gives this rock its strength. In its free form, mica is a mineral that has found its place in the radio industry and the electric power industry. But more often it is an integral part of natural conglomerates, playing a cementing role in them.

Other scientists are developing theories of smelting more fusible elements from an array of igneous rocks, and still others attach great importance to the granitization of rocks due to the influence of water and ion exchange.

All of these theories can explain the origin of specific granite deposits, but none of them is fully applicable. In any case, they cannot explain how the granite layers of the continents were formed.

Properties, application and facts

Granite is a heavy material. Its density is 2600 kg/m³, which is comparable to concrete. Its strength is also high, about 300 MPa, and granite structures have excellent bearing capacity. The melting point is more than 1200 degrees, but in the presence of water it decreases.

Human use

Granite has been used as a building material since antiquity. Now it is one of the options for outdoor decoration, and it can be found at metro stations, embankments - it is widely used in outdoor design. Unlike marble, it is more resistant to rain and frost. According to their consumer properties, granite is divided into three groups:

  1. fine-grained;
  2. medium-grained;
  3. coarse-grained.

The most popular group is the first. It is most resistant to temperature changes and water.

The latter property made this stone very popular in road construction and ritual business. Granite paving stones and curbs are more durable than concrete and asphalt, and monuments made of it cost more than marble and stainless steel ones. Recently, you can often find glued crafts made of artificial stone, but natural granite is still valued higher in the eyes of the consumer.

In interior decoration, granite products are not so popular and, moreover, are not recommended for use. From them comes an increased radiation background, recorded by a Geiger counter.

Granite crushed stone is widely used in the production of concrete. It is more expensive than limestone, but in conditions of aggressive groundwater, it is granite that shows its best side; it is more resistant to chemical aggression.

Everyone knows a lot about granite. But some facts about him are still impressive:

This stone has not yet revealed all the secrets to people, and this is especially true of its origin. Why, of all the planets in our system, it is only on Earth, so no one understood. But this does not prevent people from appreciating granite and using it.

Granite has been known since ancient times. This is one of the most famous rocks. This stone is found on almost all continents of the Earth. At times, it comes to the surface in the places of occurrence of age-old rocks, damaged by erosion. But most often, frozen magma (which granite consists of) does not reach the earth's surface and freezes at different depths, forming bodies of different sizes and configurations. It is from the destroyed rocks that the soil consists. What does it consist of?

Composition of granite

Granite contains:

  • feldspars;
  • mica;
  • quartz;
  • some dark colored minerals.

Plagigranite- in its composition, plagioclase occupies a large part, and feldspar occupies a smaller part. This type has a pinkish color.

Alaskan- feldspar dominates here, but there are few dark-colored materials in it.

And there are also: syenite, teschenite, diorite. different types have a different color. The content of feldspar is responsible for the shade of the stone, which brings a certain color to the rock: from light pink to greenish, black, silvery, golden, etc.

Granite has a grainy surface. Quartz is responsible for the grain size. It is customary to classify this rock also by grain size into:

  • fine-grained (grain size less than 2 mm);
  • medium-grained (grains 2-10 mm in size);
  • coarse-grained (grains larger than 10 mm).

Fine-grained stones are considered the best.: they are less resistant to mechanical influences, wear more uniformly during use, more resistant to weather influences, crack less when heated.

Granites with larger grains are slightly less resistant to heat: when the temperature rises above 600 degrees, they begin to grow in volume and crack. Therefore, sometimes after strong fires in houses where granite stairs were present, you can see that the stone steps are slightly cracked.

The main property of granite is its strength. What is granite? First of all, this is a very durable material that is not subject to mechanical stress, temperature changes (it is not afraid of changes over 100 degrees: it “feels” equally well at +50 degrees and at -60 degrees), it is not subject to fungal infections, it is fire resistant (melting point +700 degrees), resistant to acids. Even in the most difficult conditions, this stone remains flawless and will retain its own strength. Cutting and grinding it is carried out only with the help of diamond tools.

Characteristics:

The strength of the material depends on its moisture absorption coefficient. The value of this coefficient for this rock exceeds all other materials and depends on the place of extraction: denser layers of the deposit are a condition for having an excellent rock grade. The depth of the rock, which determines the strength and density of granite, will further determine the scope of the stone.

Granite deposits

Found on almost all continents. You can even say that this rock is the hallmark of our planet.

In Russia, the largest deposits are located in the Urals, the Far East, Eastern Siberia, the Caucasus, the Kola-Karelian (Karelian-Murmansk) region. In general, more than fifty deposits have been established where piece stone is mined. Many deposits are mined for quarrystone and crushed stone, sometimes granite blocks are also extracted from them, which are used for the manufacture of facing slabs. At times, the resulting blocks are hewn for piece stone or for architecture (the manufacture of monuments).

In the post-Soviet space, the most significant deposits are in the Zaporozhye region of Ukraine (Mokryanskoye), in the Poltava region of Ukraine (Malokokhnovskoye), in the Brest region of Belarus (Mikashevichi). In general, more than two hundred granite deposits have been developed on the territory of the former USSR.

Europe is also rich in granite deposits. For example, Italian stone (Sardinia) - a luxurious light pink color "limbar", "sardo dew", etc. (Italy is the world leader in the creation of facing materials and products). In France, the main deposits are located in Brittany, and in total more than a hundred types of this stone are mined in France. UK, Scotland. Spain has a large group of deposits of highly decorative stone, which is actively exported. Sweden, Finland (Finns are one of the largest suppliers of granite blocks to the whole world), Germany (Bavaria, Lower Saxony), Portugal.

It is known that there are huge deposits on the African continent, but due to the poor knowledge of this region, it is difficult to say what the characteristics of the rock mined there will be.

America is also replete with deposits of this "eternal" stone: in North America, mining is carried out in the states of Wisconsin, Georgia, Vermont, etc., there are deposits in Canada; in South America - Brazil, Argentina.

And in Australia, the well-known grade of blue Labrador granite is mined.

Application

Due to its strength, granite has been used since ancient times. in construction: this stone is very durable, it is practically not affected by any external irritants (even during the construction of the well-known pyramids in Egypt, granite blocks were used), so the products of this stone have been well preserved for many centuries.

The stone lends itself well to processing, it is perfectly polished, polished (you can even create a mirror surface), so it is often used in the production of facings, countertops, monuments, stairs and, of course, many their interior details.

Misconceptions about granite

For some reason, many people think that granite is very expensive for its price. The truth is that fake diamond often will have a much higher price than the running varieties of natural. Of course, this postulate does not apply to the cost of rare varieties of stone.

The opinion is also exaggerated that granite is prone to cracking when high temperatures. This is far from the case: the natural destruction of the stone lasts for many centuries.

And the most common misconception is the misconception about the radiation background emitted by the stone. In fact, this level is two times less than the established maximum permissible norms.

The result of all of the above may be the fact that granite is a stone extremely durable, beautiful and environmentally friendly.

Since ancient times, mankind has known beneficial features. This stone impressed with its structure, density, high performance. Natural granite is considered the most common rock on Earth. This is due not only to unique external, but also internal characteristics.

The natural color of granite is represented by gray, pink, black, red, green and even purple hues. Aggregate state - solid. The stone owes its origin to volcanic processes; it is minerals crystallized in magma. There is no consensus regarding its nature, the rock is attributed to metamorphic, igneous and even mixed origin.

Chemical composition

The unique properties of granite and its external characteristics allow the stone to be used in various fields of activity, mainly in construction.

A complete description of granite is contained in many specialized books. The acidic igneous structure of the rock has a granular appearance. To a greater extent, granite rock consists of feldspars, quartz, mica. Its formula is CaCO3.

The properties of granite, its color is due to the amount of spar and quartz. What color is the breed? Common shades are light gray, pink, yellow, red, green. Transparent blotches of quartz give the rock hardness, vitreousness. In nature, there are rare varieties with blue patches. They affect the overall shade of the stone, make it unique.

The crystal structure of granite stone is divided into:

  • fine-grained- grain sizes less than 5 mm;
  • medium-grained - up to 1 cm;
  • coarse-grained - from 1 cm.

Most of the granite components are variegated in color. It is almost impossible to find identical shades in nature, they simply do not exist. From the deposit, its external features depend. So, the Karelian stone is red, in Sweden there is a rare amethyst variety.

Physical and chemical properties

Physical properties granite is amazing. The stone is characterized by high thermal conductivity, frost resistance, low water absorption. Properties such as the strength of granite and its density depend on the hardness of the minerals and inclusions that make up the rock.

The main properties of granite include:

  • stability to the influence of environmental factors;
  • melting point - 1215-1260 degrees Celsius;
  • high density and specific gravity granite - an average of 3.7 g / cm3 and 2600 kilograms per cubic meter. meter respectively;
  • impressive compressive strength - 550 kg/cm2 wet and 604 kg/cm2 dry;
  • very low water absorption - 0,2%;
  • granite hardness according to Mohs table - 6-7;
  • negligible abrasion coefficient - less than 0.2 g/cm2;

How much does the breed weigh, what affects this indicator? A cube of stone weighs an average of 2600 kg, as already mentioned. But this figure depends on the mineral and is not the only possible one. Just as it is impossible to say what is the density of granite from different deposits. The true density depends on the porosity of the rock and its components.

So, the characteristics of granite directly depend on its porosity. For a natural breed, this is a very important indicator. The quality of the lining, water absorption, frost resistance, resistance to the adverse effects of acids depend on this property of the stone. The presented features are responsible for the performance and durability of the material. The higher the porosity of the rock, the lower its mass and strength.

The decorative qualities of granite tiles also directly depend on the presented indicator. The higher the porosity, the easier it happens. But at the same time, the properties deteriorate significantly.

The volumetric weight of granite, namely crushed stone, depends on the size of the fraction and is about 1500 kg per cubic meter.

Particular attention is paid to the heat capacity index. The specific heat capacity is 0.75 J/(kg×K). This is the amount of heat, the transfer of which will increase the temperature of a single mass of stone by one.

Another popular material, already of artificial origin, which has hardness, density and thermal conductivity close to granite, is porcelain stoneware. Its use in construction is now very common, especially since it costs less than natural stone.

  • The mineral composition of granite
  • The influence of the composition on the decorative effect
  • Alternative classification of granites
  • Granite Mystery

    • You will be surprised to know that granite masses make up the majority of all solid matter on planet Earth. But being the base of the earth's crust, it is almost completely hidden from our eyes. Only granite rocks and open deposits of this valuable rock give us the pleasure of using durable, beautiful material in construction and decoration. The very composition of granite and the physicochemical processes of its crystallization are also interesting and surprising.

    Many elements participated in the formation of granite rock: high pressure, temperatures of thousands of degrees and gradual cooling over thousands of years in the depths of the earth's crust. It is thanks to the unique crystallization process that we have the pleasure of admiring the unsurpassed beauty of this natural stone.

    What is the chemical composition of granite?

    In the formation of a granite massif, the strongest rock after diamond, corundum and topaz, many chemical elements are involved, among which the main ones that determine the composition of granite are distinguished:

    • Iron
    • Potassium
    • Manganese
    • Aluminum
    • Silicon
    • Sodium
    • Calcium
    • Oxygen
    • Hydrogen

    Lithium, chromium, titanium, and tungsten are also found in small quantities.

    Being part of complex chemical compounds, the listed elements form minerals, which, in the form of compressed small grains, form the familiar granite.

    The mineral composition of granite

    It is customary to call minerals homogeneous natural compounds (in simple terms, stones) that have only one substance in their chemical composition.

    In the composition of granite we find:

    Biotite is the least of it, from 5 to 10% of the total mass. Biotites are the main decoration of granite rock: they are shiny mica familiar to everyone. Their blotches just give the eye magical overflows when you change the viewing angle. The formula of biotite is very complex, it contains potassium, manganese, iron, aluminum, hydrogen and oxygen.


    Muscovite (this is also mica) is also found in a small amount in the composition of granite - a stone of various shades, from milky yellow to silver and green.

    Quartz - those who remember chemistry lessons well will immediately say: this is “natural glass”, or silicon oxide. Quartz makes up approximately 25-35% of the substance of granite rock.


    Feldspars are a collective group that includes acidic plagioclases and predominantly potassium feldspars. The percentage of this group of stones is the largest and ranges from 60 to 65%. Minerals of this group got into the composition of granite not in vain: this is the most common stone, accounting for approximately 50% of the entire mass of the earth's crust.


    Plagioclase is a rather interesting mineral in the composition. In its pure form, it is a stone with sharp oblique cleavage planes, thanks to which the Greeks called it: “oblique stone”. Its formula is also very interesting: Ca. It turns out that for the most part it's just oxidized metals and silicon.


    The potassium feldspar group is four minerals that have the same formula KAlSi 3 O 8, but, thanks to different conditions crystallization, which received different ordering of the crystal lattice.

    What is included in the composition of granite can be roughly determined by its color and texture: after all, each deposit contains an absolutely unique rock with its own unique mineral structure and chemical composition.

    How does the composition of granite affect its decorative effect?

    There are a huge variety of brands of granite, and each stone has a unique color, structure, grain size and texture.

    Geologists conditionally divide granite rocks into groups:

    • Plagiogranites - in the mineral composition of granite, it is plagioclases that are "responsible" for the light gray color of the stone. A small amount of feldspars can only slightly color the stone in a light pink hue.
    • Alaskites - the predominantly mineral composition of granite is composed of potassium-sodium feldspars with small admixtures of biotites. Alaskans in their pure form are pink in color.

    However, we know in practice that the color range of granite rocks is much wider. That's right, the most diverse colors and shades are obtained due to minor impurities of metal oxides, which color minerals in colors unusual for them.

    Thanks to such "additives" in the mineral composition of granite, we can see rocks of all colors:

    • Black - brands Absolut Black or Black Galaxy, Gabbro.
    • - Imperial Red, Kapustinsky, Leznikovsky.
    • Yellow - Sunset Gold, Crystal Yellow.
    • Green - Green Ukraine, Maslavsky (Verde Oliva), Butterfly Green.
    • Blue - Ultramarine, Sodalite Blue, Azul Macaubas.
    • Colored - coarse-grained or fine-grained, with the most unexpected combinations of colors. For example, Didkovichsky, Yuzhno-Sultaevsky, Bainbuk Brown.

    A huge variety of natural stones in deposits around the world is obtained due to the unique chemical composition of granite. Nature created crystallized masses according to special "recipes" and for each brand the mineral composition of granite is completely unique.

    What else is included in granite?


    An alternative classification of granites according to the principle of what is included in granite - magma or sedimentary rocks, is widely used abroad and boils down to the allocation of 4 groups:

    • S - it is believed that the granitic rocks of this group are composed of melting products of metasedimentary substrates.
    • I - this group consists of melted metamagmatic substrates.
    • M - crystallized tholeiite-basalt magmas.
    • A - melted lower crustal granulites are added to the differentiates of magma of alkaline-balsatoid composition.

    Scientists are still hotly arguing about the origin of the really amazing stone, which, by the way, is found only on Earth. Until now, the physicochemical processes of crystallization, as well as the true origin of the crystallized masses, have not been thoroughly studied.

    But be it modified sedimentary rocks or frozen igneous masses, granites amaze with their unique beauty and high strength, due to which they are widely used in decorative finishes.

    The great mystery: why do the minerals in granite have such a ratio?

    Another amazing fact that baffles almost all geologists and chemists can strike anyone. After all, if we follow the generally accepted theory of melting of solid crustal matter, when a low-potassium granite material is formed, which makes up only 20% of the total mass, 80% of the solid residue should remain, in which there is no water. These should be minerals: pyroxene, the same plagioclase or garnet. But no such layers were found during research!

    What is hidden in the depths of the earth's crust with huge layers of granite rock, one can only guess. One thing is undeniable: the composition of granite is truly unique, if scientists have not yet been able to find similar rocks on other planets.