Granite - description and properties of a healing stone. What is granite and what properties does it have? Granite stone description for kids

All these varieties of granite material are used for different purposes:

• from granite blocks construction objects and monuments are erected;
• plates used in the exterior and basement of buildings, as well as wall coverings and indoors;
• - for paving streets and roads;
• rubble and crumb applicable in finishing work, decorative design and landscape design (), used in the production of concrete to achieve high strength indicators.

Granite finishes can transform any building, both inside and out. Using granite stones of various shades, ranging from deep red to pearl gray, designers successfully use the mineral for interior decoration. Competently combining it with wood, metal or ceramics, they create amazing objects - mirrored kitchen countertops, country gazebos, flower beds in the style of a Japanese rock garden, monumental polished stairs and other masterpieces.

A little about stone processing

As mentioned above, despite the hardness of natural rock, it is quite easy to process, and therefore the question “what can be made of granite” has dozens of solutions. It can be cut, modify the surface of the stone by grinding to the desired state, and also play with shades - make it lighter or darker, for which they resort to special processing technologies.

Raw stone looks natural and absorbs light well, but slabs polished and polished to a mirror shine emphasize the advantages of this material and the beauty of mica inclusions. When processing the rock by chipping, an interesting relief is obtained with an artificial effect of the play of chiaroscuro, and some varieties of gray stone after heat treatment receive a milky white hue.

This stone has attracted people since ancient times, but now with the improvement of stone processing technologies, the use of granite in the construction of office buildings and private houses has become even more accessible.

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Granite rock

English name: Granite

Minerals in the rock composition Granite: BiotiteQuartzMuscovitePlagioclaseFeldspar

Granite- acidic plutonic rock of the normal series from the granite family. Consists of quartz, plagioclase potassium feldspar and micas - biotite and/or muscovite. These rocks are very widespread in the continental crust. The effusive analogues of granites are rhyolites.

The role of granites in the structure of the upper shells of the Earth is enormous, but unlike the magmatic rocks of the basic composition (gabbro, basalt, anorthosite, norite, troctolite), analogues of which are common on the Moon and terrestrial planets, this rock is found only on our planet and has not yet been established. among meteorites or on other planets of the solar system. Among geologists, there is an expression "Granite is the visiting card of the Earth."
On the other hand, there are good reasons to believe that the Earth arose from the same substance as the other terrestrial planets. The primary composition of the Earth is reconstructed as close to that of chondrites. Basalts can be smelted from such rocks, but not granites.
These facts about granite led the very first petrologists to pose the problem of the origin of granites, a problem that has attracted the attention of geologists for many years, but is still far from a complete solution. A lot of scientific literature has been written about granite.
The author of one of the first hypotheses about the origin of granites was Bowen, the father of experimental petrology. On the basis of experiments and observations of natural objects, he established that the crystallization of basalt magma occurs according to a number of laws. The minerals in it crystallize in such a sequence (the Bowen series) that the melt is continuously enriched in silicon, sodium, potassium and other fusible components. Therefore, Bowen suggested that granitoids may be the last differentiates of basaltic melts.

Geochemical classifications of granites

Widely known abroad is the classification of Chappel and White, continued and supplemented by Collins and Valen. It distinguishes 4 types of granitoids: S-, I-, M-, A-granites. In 1974, Chappell and White introduced the concepts of S- and I-granites, based on the fact that the composition of granites reflects the material of their source. Subsequent classifications also largely adhere to this principle.
S - (sedimentary) - melting products of metasedimentary substrates,
I - (igneous) - melting products of metamagmatic substrates,
M - (mantle) - differentiates of tholeiite-basalt magmas,
A - (anorogenic) - melting products of lower crustal granulites or differentiates of alkaline-basaltoid magmas.

The difference in the composition of the sources of S- and I-granites is established by their geochemistry, mineralogy, and composition of inclusions. The difference in sources implies also the difference in the levels of melt generation: S is the supracrustal upper crustal level, I is the infracrustal deeper and often more mafic. Geochemically, S- and I have similar contents of most petrogenic and rare elements, but there are also significant differences. S-granites are relatively depleted in CaO, Na2O, Sr, but have higher concentrations of K2O and Rb than I-granites. These differences are due to the fact that the source of S-granites has passed the stage of weathering and sedimentary differentiation. The M type includes granitoids, which are the final differentiate of tholeiite-basalt magma or the melting product of a metatholeiite source. They are commonly known as oceanic plagiogranites and are characteristic of modern MOR zones and ancient ophiolites. The concept of A-granites was introduced by Ebi. He showed that they vary in composition from subalkaline quartz syenites to alkaline granites with alkaline dark colors and are sharply enriched in incoherent elements, especially HFSE. According to the conditions of education can be divided into two groups. The first, characteristic of oceanic islands and continental rifts, is a product of the differentiation of alkaline-basaltic magma. The second one includes intraplate plutons not directly associated with rifting, but confined to hot spots. The origin of this group is associated with the melting of the lower parts of the continental crust under the influence of an additional heat source. It has been experimentally shown that during the melting of tonalite gneisses at Р=10 kbar, a melt enriched in fluorine in terms of petrogenic components is formed, similar to A-granites and granulite (pyroxene-containing) restite.

Geodynamic settings of granitic magmatism

The largest volumes of granites are formed in collision zones, where two continental plates collide and the continental crust thickens. According to some researchers, a whole layer of granite melt is formed in the thickened collisional crust at the level of the middle crust (depth 10–20 km). In addition, granitic magmatism is characteristic of active continental margins (Andean batholiths) and, to a lesser extent, of island arcs.

In very small volumes, they are also formed in the mid-ocean ridges, as evidenced by the presence of segregations of plagiogranites in ophiolite complexes.

• hornblende
• biotite
• hornblende-biotite
• two-mica
• mica
• hypersthenic (charnockite)
• augite
• graphite
• diopside
• cordierite
• malacolitic
• pyroxene
• enstatite
• epidote

According to the varieties of potassium feldspar, varieties are distinguished:

• microcline
• orthoclase

The texture of granites is massive with very little porosity, characterized by a parallel arrangement of mineral components. According to the size of the grains that make up the rock of minerals, three structures of granite are distinguished: fine-grained with grain sizes up to 2 mm, medium-grained - from 2 to 5 mm and coarse-grained - over 5 mm. The grain sizes strongly influence the building properties of granite rocks: the finer the grain sizes, the higher the strength characteristics and durability of the rocks.
These rocks are dense, durable, decorative, well polished; have a wide range of colors from black to white. Granite is characterized by bulk density of 2.6-2.7 t/m3, porosity is less than 1.5%. The compressive strength is 90-250 MPa and higher, in tension, bending and shear - from 5 to 10% of this value.
Granite is a clear-crystalline coarse, medium or fine-grained massive igneous rock formed as a result of slow cooling and solidification at a great depth of a magmatic melt. Granite can also be formed during metamorphism, as a result of the processes of granitization of various rocks. Individual granite massifs are often attributed either to igneous, or to metamorphic, or even to mixed origin.
The color is predominantly light gray, but pink, red, yellow and even green (amazonite) varieties are also often called granite.
The structure is usually uniform-grained, most of the grains have an irregular shape due to constrained growth during mass crystallization. There are porphyritic granite massifs, in which large crystals of feldspars, quartz and mica stand out against the background of a fine- or medium-grained groundmass. The main rock-forming minerals of granite are feldspar and quartz. Feldspar is represented mainly by one or two types of K-feldspar (orthoclase and/or microcline); in addition, sodic plagioclase, albite or oligoclase, may be present. The color of granite, as a rule, determines the mineral predominant in its composition - potassium feldspar. Quartz is present in the form of glassy fractured grains; usually it is colorless, in rare cases it has a bluish tint, which can take on the entire breed.
In smaller quantities, granite contains one or both of the most common minerals of the mica group - biotite and / or muscovite, and in addition, scattered dissemination of accessory minerals - microscopic crystals of magnetite, apatite, zircon, allanite and titanite, sometimes ilmenite and monazite. Prismatic hornblende crystals are observed sporadically; garnet, tourmaline, topaz, fluorite, etc. may appear among the accessories. With an increase in the content of plagioclase, granite gradually turns into granodiorite. With a decrease in the content of quartz and potassium feldspar, granodiorite undergoes a gradual transition to quartz monzonite, and then to quartz diorite. Rocks with a low content of dark-colored minerals are called leucogranites. In the marginal zones of granite massifs, where the rapid cooling of magma retards the growth of crystals of rock-forming minerals, granite gradually turns into fine-grained varieties. Granite-porphyries include a variety of granite, consisting of individual large grains (phenocrysts), immersed in a finer-grained groundmass, which consists of small, but still visible to the eye crystals. Depending on the presence of secondary, predominantly dark-colored, minerals, several varieties of granite are distinguished, for example, hornblende, muscovite, or biotite.
The main form of occurrence of granites is batholiths, which are huge massifs with an area from hundreds to thousands of square kilometers and a thickness of 3-4 km. They can occur in the form of stocks, dikes, and other intrusive bodies. Sometimes granitic magma forms layer-by-layer injections, and then granite forms a series of sheet-like bodies, alternating with layers of sedimentary or metamorphic rocks.

Application

The massiveness and density of granite, its wide textural possibilities (the ability to take on a mirror polish, in which an iridescent play of mica inclusions appears in the light; the sculptural expressiveness of an unpolished rough stone that absorbs light) make granite one of the main materials of monumental sculpture. Granite is also used to make obelisks, columns, and as cladding on various surfaces.

The most ancient material, the constant companion of man, elegant and solid, expressive and diverse, massive and eternal - these qualities that granite possesses are the best material for creating a human habitat. Your interior can become cold or cozy-warm, defiantly luxurious or modest, light or dark.

Origin and classification of rocks

Nature has created it so unique and diverse that each product, fragment, lined surface is unique. The main advantage inherent in granite is its natural hardness. Excellent material for external finishing of facades, steps and floors. A wide range of colors opens up unlimited possibilities for designers. Most breeds have low abrasion and water absorption. Under modern processing conditions, granite is cut and polished with a diamond. In addition, you can achieve its mirror polishing. It is a stone used in construction, which is the most resistant to inclement weather, has a very high compressive strength (800 to 2.200 kg/sq.cm).

It is used for facing columns, balconies, stairs, monuments, furniture, etc. Granite rocks - in common speech, in a technical and commercial sense, this name defines igneous rocks - both intrusive and effusive, with a hardness and workability comparable to granite . Their resistance to crushing and pressure is in most cases also very high. Still gneisses formed by rocks of volcanic origin, which have the same or slightly different mineralogical composition as granites, are defined as granitic rocks. That is, granite rocks used as building materials include, in addition to scientifically defined granites, syenite, diorite, gabbro, porphyry, liparite, trachyte, andesite, basalt, diabase, feldspathoid, gneiss, sericio, slate quartzite, serpentine and others. varieties and subspecies of the above mentioned structures. Many of the breeds listed, from Trachytes onwards, have commercial names determined by their use or manufacturer. No one would sell trachyte, gneiss, sericio, slate quartzite, or serpentine as granite, also because of their characteristic appearance, which is often impossible to confuse with anything else.

The rock determines here only the characteristics of hardness and workability, which are very different from those of marble. Obscurity and ambiguity between commercial, technical and scientific names can arise, on the contrary, between granites, syenites, diorites, porphyries due to their appearance, which can be very similar to the layman and easily leads to deception, as due to old names, and because of the many stratifications in different types of rocks of the same family, or due to other reasons.

Rock Properties

• Rock type: Igneous rock
• Color: light grey, pink, red, yellow, greenish
• Color 2: Gray Red Yellow Green
• Texture 2: massive porphyritic
• Structure 2: fine-grained medium-grained coarse-grained
• Origin of name: from granum - grain

Rock Photo

Related Articles

• General information about granite massifs
  The Egyptians, in the construction of their famous pyramids, used very hard and massive rocks as a basis.
• More about the composition of granites
  The main rock-forming minerals of granites are feldspar and quartz. Feldspar is represented mainly by one or two types of potassium feldspar
• Application of granites
  Granite is one of the most dense rocks. In addition, it has low water absorption and high resistance to frost and pollution. That is why it is used both indoors and outdoors. In the interior it is used for finishing walls, stairs, creating countertops, columns and fireplaces.
• eternal stone
  The advantages that natural stone has in construction and sculpture are, first of all, strength and durability. In particular, the first signs of visible destruction of the fine-grained stone begins to appear after about four hundred to six hundred years.

Granite Rock Deposits

Origin of the word granite

granite

French - granite.

Latin - granum (grain).

In Russian, the word has been known since the middle of the 18th century, and it has been noted in dictionaries since 1762 (by Lichten).

Stone granite: rock

Presumably borrowed from French, where granite came from Italian, where granito is "granite", and as an adjective - "grainy", "strong", "hard". In Italian, the word comes from the Latin granum. The Latin original became the basis for borrowing by other European languages: German Grant, English granite, etc.

The modern meaning of the Russian word "granite" is "hard rock of a granular structure used in construction."

Related are:

Bulgarian - granite.

Czech - granit.

Derivative: granite.

The origin of the word granite in the etymological online dictionary of Semyonov A.V.

Granite. A word very close in origin from "granum" - "grain": "granular stone". It was formed not in the Latin language of antiquity, but in the dictionaries of its heirs - Italian ("granito") and French ("granit") languages, from where it came to us.

But what a Russian it has become, this word:

Neva sovereign current,
Its coastal granite ...

The origin of the word granite in the etymological online dictionary of Uspensky L.V.

granite through it. Granit or French. granite from it. granito, literally "grainy": lat. grānum; see Hamilsheg, EW 482.

The origin of the word granite in Fasmer's online etymological dictionary M.

Mark typos and other inaccuracies with the cursor, press Ctrl + Enter and send to us!

See also: meaning of the word granite in explanatory dictionaries.

Origin and classification of rocks

Any natural stone is "a rock, a natural formation consisting of individual minerals and their associations."

Granite - characteristics and properties of the rock

Petrography is the study of the composition, origin, and physical properties of rocks. According to her, all breeds by origin last for three main groups:
1. Igneous ("primary" rocks)

- formed directly from magma - a molten mass of predominantly silicate composition, as a result of its cooling and solidification. Depending on the conditions of solidification, deep and outflowing are distinguished.
deep
arose as a result of the gradual cooling of magma at high pressure inside the earth's crust. Under these conditions, the constituents of the magma crystallized, due to which massive dense rocks with a fully crystalline structure were formed: granite, syenite, labradorite and gabbro.
poured out
formed as a result of a volcanic eruption of magma, which quickly cooled on the surface at low temperature and pressure. There was not enough time for the formation of crystals, so the rocks of this group have a latent or finely crystalline structure with an abundance of amorphous glass with high porosity: porphyries, basalts, travertine, volcanic tuffs, ashes and pumice.

Granite(from the Latin granum, grain) is the most common rock. Granite has a pronounced granular-crystalline structure and consists mainly of feldspars, quartz, mica and other minerals.

According to the size of the grains, 3 structures of granite are distinguished: fine-grained, medium-grained, coarse-grained. The color of granite can be very different. Gray granite is most commonly found, ranging from light to dark with varying hues, but there are also pink, orange, red, bluish-gray and sometimes bluish-green granite. Exceptionally rare granite with blue quartz. In decorative terms, the most valuable are fine-grained light gray with a blue tint, rich dark red and greenish-blue varieties of granite.

2. Sedimentary (or "secondary" rocks)

- are called secondary, as they were formed as a result of the destruction of igneous rocks or from the waste products of plants and animal organisms.
They can be in the form of chemical precipitation, which are formed during the drying of lakes and bays, when various compounds precipitate. Over time, they turn into limestone tuffs, dolomite. A common feature of these rocks is porosity, fracturing, and solubility in water.
There are also clastic sedimentary rocks. These include cemented sandstones, breccias, conglomerates and loose: sands, clays, gravel and crushed stone. Cemented deposits were formed from loose deposits as a result of natural bonding, cementing. For example, sandstone is made from quartz sand with lime cement, breccia is made from cemented crushed stone, and conglomerate is made from pebbles.
Rocks of organic origin are also known, these are limestones and chalk. They are formed as a result of the vital activity of animals and plants.

Sandstone

For geologists and petrographers, it is a clastic rock consisting of cemented sand. There are gray, green, red, yellow, brown and brown. Siliceous sandstones are considered the most durable.
Basically, sandstones are not able to acquire a polished texture, so they usually use a chipped or sawn texture, and sometimes polished. Sandstones lend themselves well to hexing and diamond processing.
Fine-grained red, chocolate brown and green varieties of sandstone are considered decorative, which are successfully used for exterior cladding. In Moscow and St. Petersburg architectural monuments built in the 19th and early 20th centuries, facings made of Polish sandstone in gray-green, yellow and pink shades are well preserved. Assumption Square of the Kremlin is lined with Lyubertsy sandstone.
Sandstone is a rather porous material, so it is undesirable to use it for finishing elements in contact with water. It is also not recommended to use it on basement structures.

3. Metamorphic (modified rocks)

- formed by the transformation of igneous and sedimentary rocks into a new type of stone under the influence of high temperature, pressure and chemical processes.

Among the metamorphic rocks, massive (granular) are distinguished, these include marble and quartzite, as well as schistous ones - gneisses and shales.

Marble

The name "marble" comes from the Greek marmaros, shiny. This is a granular-crystalline rock, which was formed in the bowels of the Earth as a result of recrystallization of limestone and dolomite under the influence of high temperatures and pressure. In construction, not only this stone, but also other dense transitional carbonate rocks are often called marble. These are, first of all, marble-like or marbled limestones and dolomites.

Quartzite

These are fine-grained rocks that were formed during the recrystallization of siliceous sandstones and consist mainly of quartz.

Quartzite comes in gray, pink, yellow, crimson red, dark cherry, and sometimes white.
Quartzite is considered a highly decorative stone, especially crimson red and dark cherry. The texture of the "rock" significantly brightens the general background of this stone, which is often used by combining such products with polished contrasting colors.
Quartzite has a very high hardness and is a difficult material to cut, but it accepts a very high quality polish.
Often used in the construction of unique structures. It was used in the construction of the Church of the Savior on Blood. It has also been used as a ritual stone for centuries. The sarcophagi of Napoleon and Alexander II, the upper part of Lenin's mausoleum are made of it.

Slate

A dense and hard rock that was formed from highly compacted clay, partially recrystallized under high and one-sided pressure (from top to bottom, for example). It is characterized by an oriented arrangement of rock-forming minerals and the ability to split into thin plates. The color of shales is most often dark gray, black, gray-brown, red-brown.
Slate is a durable material, it can be processed (exfoliates into thin plates), some types can also be polished. However, more often it is used without processing at all, since the split surface is very decorative.
Slate is used in both exterior and interior cladding. This stone was widely used in well-known architectural monuments (the floors of St. Isaac's Cathedral in St. Petersburg are partly made of slate).

4. Semi-precious stones.

These can include, mainly rocks, called "decorative and ornamental stones." These are jasper, onyx, opal, malachite, lapis lazuli. They are much rarer than ordinary stone and are valued more. However, it is expensive to veneer large areas with them, therefore, most often small elements are trimmed with these stones: details of columns, window sills, bathrooms ...

One of the most common decorative and ornamental stones is onyx (“nail” in Greek). Onyx has a layered or radical-radiant structure. Onyx color - white, light yellow, yellow, brown, dark brown, pale green. Striped pattern - alternating stripes of different shades. Most marble onyxes are translucent, sometimes to a depth of 30…40 mm. Onyx is well processed by cutting and grinding tools and takes high quality polishing.

Composition, origin and properties of granite. Color spectrum

Granite - in a few words about the popular breed

Name from lat. granum - grain.

The structure of granite is crystalline-granular. According to the chemical composition, granites are rocks rich in silicic acid, enriched in alkalis, more or less poor in magnesium, iron and calcium.

How and from what are granite rocks formed?

Composition (average values): feldspars - 60-65% (orthoclase and plagioclase, with the former predominating), quartz - 25-30% and mafic minerals - 5-10% (mainly biotite, much less often hornblende and tourmaline ). Granites are very strong rocks: compressive strength is 1200-1800 kg / cm², rarely decreasing to 1000 and sometimes rising to 3000 kg / cm².

Origin of granite

The origin of granite is magmatic: it is a product of crystallization of acidic magma in the deep zones of the earth's crust. In the later epochs of the Earth's development, especially in connection with mountain-building processes, granites were formed from masses of sedimentary, clayey and clastic rocks, which, due to tectonic movements, fell into deeper horizons of the earth's crust. Under the influence of high pressures and temperatures in combination with hot gases ("volatile components"), the sediments were subjected to melting (remelting) with the formation of granites.

Composition of granite

According to the content and nature of dark-colored minerals, the following varieties of granite are distinguished: alaskite (not containing dark-colored); leucocratic granite (leucogranite) with a reduced content of mafic; biotite garnet (the most common; dark-colored ones are represented by biotite, their content is 6-8%); two-mica granite (with biotite and muscovite); hornblende and hornblende-biotite granite (with hornblende instead of biotite or along with it); alkaline granite (with aegirine and alkaline amphiboles; feldspars - orthoclase or microcline and albite).

According to structural and textural features, varieties are distinguished: porphyritic granite - contains elongated or isometric inclusions, more or less significantly different in size from the minerals of the ground mass (sometimes reaching 5-10 cm) and usually represented by orthoclase or microcline and quartz; pegmatoid granite - a uniformly granular granite rock with a size of feldspar and quartz segregations of 2-3 cm; rapakivi, or Finnish granite, is a porphyritic granite in which abundant rounded inclusions of red orthoclase 3-5 cm in size are surrounded by a border of gray or greenish-gray oligoclase, and the aggregate of grains of orthoclase, plagioclase, quartz, biotite and hornblende serves as the bulk; gneissic granite - uniformly and usually fine-grained granite, in which there is a general roughly parallel orientation of mica flakes or prismatic grains of hornblende.

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Origin of granite, conditions of occurrence

Granite (Italian granito, from Latin granum - grain), an igneous rock rich in silica. One of the most common rocks in the earth's crust. It consists of potassium feldspar (orthoclase, microcline), acid plagioclase (albite, oligoclase), quartz, as well as mica (biotite or muscovite), amphibole and, rarely, pyroxene. The structure of granite is usually full-crystalline, often porphyritic and gneiss-banded. Granite prevails among intrusive rocks and occupies a significant place in the geological structure of the Urals, the Caucasus, Ukraine, Karelia, the Kola Peninsula, Central Asia, Siberia, etc. Granite intrusions have an age from Archean to Cenozoic. Usually, granites occur among rocks in the form of batholiths, laccoliths, stocks, veins, etc. During the formation of granite bodies and their cooling, a regular system of cracks arises, due to which granite in natural outcrops has a characteristic parallelepipedal, columnar, or sheet-like separateness.

History of the stone

At the end of the 18th century, scientists seriously believed that granites were formed by the precipitation of crystals on the bottom of an ocean filled with sea water. This hypothesis was supported by the scientific school of Neptunists, headed by the German geologist A.G. Werner (1749-1817). However, already at the beginning of the 19th century, the fallacy of such an interpretation became obvious, and it gave way to the concept of plutonists, who provided convincing evidence that granites arose as a result of cooling and solidification of silicate melts - magmas rising from the depths of the Earth. The first to formulate this idea was the Englishman J. Hutton (1726-1797). In the middle of the 20th century, the origin of granites became the subject of a new discussion. As an alternative to the concept of the igneous nature of these rocks, the idea was put forward that granites can be formed by transforming (transforming) rocks of a different composition when they interact with hot aqueous solutions, which bring the components necessary to create granite and remove (dissolve) "extra" chemical elements. The idea of ​​granitization of the earth's crust under the influence of hot solutions continues to develop today.

Early discussions about the nature of granites took place at a time when the composition and conditions of occurrence of these rocks were known only in general terms, and the physicochemical processes that could lead to their formation remained unexplored. In the second half of the 20th century, the situation changed radically. By that time, a large amount of information had been accumulated on the position of granites in the earth's crust, and the composition of these rocks had been studied in detail. Disputes about the possible origin of granites from the standpoint of common sense have given way to rigorous thermodynamic calculations and direct experiments that reproduce the origin of granite magmas and their subsequent crystallization. Naturally, new problems arose, but the level of scientific discussion became completely different.

Bowen became the author of one of the first hypotheses about the origin of granites. On the basis of experiments and observations of natural objects, he established that the crystallization of basalt magma occurs according to a number of laws. The minerals in it crystallize in such a sequence (the Bowen series) that the melt is continuously enriched in silicon, sodium, potassium and other fusible components. Therefore, Bowen suggested that granites may be the last differentiates of basaltic melts.

General information about granite

The term "granite" reflects the granular structure of the rock, clearly visible to the naked eye (from lat. granum - grain).

Composition and origin of granite

In ancient times, this word was called any coarse-grained rocks. In modern geological literature, the term "granite" is used in a narrower sense. They designate full-crystalline rocks, which consist of Ca-Na and K-Na feldspars (CaAl2Si2O8-NaAlSi3O8 and KAlSi3O8-NaAlSi3O8), quartz (SiO2) and a certain amount of Fe-Mg silicates, most often it is dark mica - biotite: K ( Mg, Fe, Al)3(Al, Si)4O10(OH, F)2. Feldspars in total make up about 60% of the rock volume, quartz - at least 30%, and Fe-Mg silicates - up to 10%. The bulk chemical composition of granites is characterized by a high content of silica (SiO2), which ranges from 68-69 to 77-78 wt.%. In addition, granites contain 12-17 wt.% Al2O3, 7-11 wt.% of the sum of CaO + Na2O + K2O, and up to several mass percent of the sum of Fe2O3 + FeO + MgO. The size of mineral grains in granites usually varies from 1 to 10 mm. Individual crystals of pink K-Na feldspar often reach several centimeters in diameter and are clearly visible on the surface of polished granite slabs.

Photo: Alan Levine

Conditions of occurrence of granites

Granites are rocks characteristic of the upper part of the continental crust. They are unknown at the bottom of the oceans, although on some oceanic islands, for example in Iceland, they are quite widespread. Granites have been formed throughout the geological history of the continents. According to isotope geochronology, the oldest rocks of granitic composition date back to 3.8 billion years, and the youngest granites are 1-2 million years old.

Quartz-feldspar granite rocks form bodies that initially did not come out on the surface. According to geological data, the upper contacts of granite bodies at the time of formation were located at a depth of several hundred meters to 10-15 km. Currently, the granites are exposed due to the subsequent uplift and erosion of the roof rocks. According to statistical calculations, granites make up about 77% of the volume of all igneous bodies that have solidified at a depth in the upper part of the continental crust.

There are displaced and non-displaced granite bodies. Displaced granites arose as a result of the intrusion of granitic magma and the subsequent solidification of magmatic melt at one or another depth. The shape of bodies composed of displaced granites is very diverse - from small veins 1-10 m thick to large plutons, occupying hundreds of square kilometers in area and often merging into extended plutonic belts. Along with relatively thin granite plates (< 1-2 км по вертикали) известны плутоны, уходящие на глубину нескольких километров. Например, Эльджуртинский плутон на Северном Кавказе пересечен четырехкилометровой скважиной, которая не достигла нижнего контакта гранитов. В Береговом хребте Перу в Южной Америке граниты обнажены в интервале более 4 км и уходят на неизвестную пока глубину.

The main evidence for igneous displaced granites is as follows. First, the formation of granite bodies is accompanied by local deformations of the surrounding rocks, which indicate the active intrusion of the granite melt. Secondly, near contacts with granites, host rocks underwent transformations caused by heating. Judging by the mineral associations that arose during this process, the initial temperature of the granitic bodies was higher than the solidification temperature of the granitic magma, which, therefore, was introduced in a liquid state. Finally, and at present, volcanic eruptions are taking place, bringing magmas of granitic composition to the surface.

Unlike the displaced granites, which solidified well above the region of their origin, the undisplaced granites crystallized approximately at the very place where they originated. If the displaced granites are usually homogeneous rocks that fill certain volumes, then the non-displaced granites are more often found in the form of bands, lenses, spots measured in millimeters and centimeters in diameter, which are interspersed with rocks of a different composition. Such formations are called migmatites (from the Greek migma - a mixture). There are no clear signs of active mechanical intrusion of granitic material in migmatites; one often gets the impression that this material passively replaces the original substrate. Hence, ideas arose about the granitization of certain sections of the earth's crust. Migmatites were formed at a depth of 5-7 km or more. Their predominant part was formed in the Precambrian time, more than 600 million years ago; Many migmatites are billions of years old.

Migmatites and larger bodies of ancient undisplaced granites are often considered as solidified zones of granitic magma generation brought to the modern day surface as a result of the subsequent uplift of the earth's crust. Since deeply eroded migmatite complexes are exposed in some places, and shallower displaced granites are exposed in others, it is not possible to trace direct relationships between them.

Granite magma is a general term used to describe magma that is similar in composition to granite, that is, containing more than 10% quartz. Granites are associated with volcanic areas, continental shields and orogenic belts. There are two possible theories of the origin of granite. One of them, known as the igneous theory, states that granite is derived from the differentiation of granitic magma. The second, known as the granitization theory, states that granite is formed "in situ" by ultrametamorphism. There is evidence that these theories are correct, and the current understanding is that granite is produced by both processes, and in many cases, a combination of the two.

Composition of granite magma sources

The quantitative relationships between quartz and feldspars in granites depend on several variables, including pressure. Taking into account the theoretically calculated and experimentally confirmed dependences, it was found that the sources of granitic magmas, corresponding in composition to actually observed rocks, are located in the continental crust at a depth of 10-15 to 30-40 km, where the lithostatic pressure is 300-1000 MPa.

The formation of low-potassium essentially plagioclase granites is associated with partial melting of less silicic quartz-plagioclase-amphibole igneous rocks occurring in the lower part of the continental crust. These rocks themselves were once smelted from the material of the Earth's upper mantle, which lies at a depth of more than 40 km. The melting reactions leading to the formation of granites are reduced to the dehydration of amphibole when the crustal substance is heated and the transition to a melt of quartz and part of plagioclase. The possibility of obtaining low-potassium granitic magmas in this way has been proven by numerous experiments. It is shown that partial melting of quartz-garnet-pyroxene rocks, which are stable in zones of higher pressure, leads to a similar result. The model is in good agreement with the geochemical features of low-potassium granites and the initial Pb, Sr, and Nd isotopic composition, which corresponds to the isotopic signatures of the mantle material. Following I.V. Belkov and I.D. Batieva, low-potassium granites can be designated as primary crustal (abbreviated P-granites from the English term "primary crustal granites"). In all epochs of granite formation, these granites appear first and increase the volume of granitic matter in the earth's crust. This genetic group also includes the most ancient granitic rocks with an age of about 3.8 billion years.

Low-potassium P-granites, formed in the early stages of geological history, occupy a significant part of the continental crust and later repeatedly experienced various transformations, including repeated melting. As a result, granites of various compositions arose, which, in the classification of Australian petrologists B. Chappell and A. White, were identified as I-granites (igneous granites). The term emphasizes the igneous nature of the crustal material involved in partial melting.

I-granites are contrasted with S-granites (sedimentary granites), the source of which, according to Chappell and White, are metamorphosed (transformed under conditions of high temperatures and pressures) sedimentary quartz-feldspar rocks. Unlike moderately aluminous I-granites with not very high potassium contents, S-granites are rich in potassium and supersaturated with alumina, that is, (2Ca + Na + K)< Al, в них много слюды и часто содержатся высокоглиноземистые минералы. S-граниты лишены магнетита, что указывает на восстановительные условия зарождения и кристаллизации гранитных магм. Это обусловлено обогащением метаморфизованных осадочных пород графитом. Расплавы, затвердевающие в виде S-гранитов, обогащены водой и имеют относительно низкую начальную температуру. Они затвердевают на довольно большой глубине и, как правило, не имеют вулканических аналогов.

A-granites (alkaline, anhydrous, anorogenic granites) are also distinguished as a special genetic group. These rocks are enriched in alkali metals (Na and K) and contain relatively little aluminum, so that often (2Ca + Na + K) > Al. Judging by the composition of minerals, the melts were poor in water but enriched in fluorine. If I- and S-granites are distributed in mobile geological belts, then A-granites gravitate towards stable blocks of the earth's crust. The sources of A-granites are quartz-feldspar rocks of the earth's crust, which have undergone transformations under the influence of deep alkaline solutions. It is possible that these rocks were originally "dry" solid remains from previous episodes of partial melting; a significant part of the water was removed with the early portions of the granite melt.

Rice. Fig. 1. Compositions of natural granites according to O. Tuttle and N. Bowen, 1958. The diagram reflects the distribution density of points characterizing the compositions of granites. The inner dark region corresponds to the density maximum.

Granite is the main element of the continental crust. The stone is known for its hardness, after being mined from a quarry, it can exist almost unchanged for hundreds of years in the open air. Changes in temperature, precipitation do not affect the appearance and hardness of this material. Thanks to the hardness of this material, granite buildings and sculptures have existed for thousands of years - obelisks were built from this material, figures of animals and people were carved in ancient Egypt. We present interesting facts about granite.

Yosemite Wildlife Sanctuary, USA

Physical properties

Translated from Latin, "granum" means "grain". The stone is a mixture of feldspar and quartz, and other minerals may also be included. In the distant past, due to volcanic activity, these substances were in a molten state, cooling slowly, they formed crystals. Since these crystals are small, they give granite its grainy texture.

The material conducts sound well. The speed of propagation of sound waves is 10 times greater than in air.

Granite is 2.5 times heavier than water.

The most common granite is black or grey. But this stone exists in many other colors - it is green, yellow, red, orange. The color depends on how much spar is present in the stone, as well as the type of spar. When white feldspar is mixed with white plagioclase, a white or gray technical granite is obtained, which is called granodiorite.

The hardest granite has a fine-grained structure. In the open air, this material can stand without visible changes for up to five thousand years. Of course, products made from this material can stand for many thousands of years, only temperature changes, exposure to moisture can somewhat affect the structure, microcracks appear, which can expand over time.

There is an artificial substitute - porcelain stoneware. It is made in various colors and textures. This material is not so strong (Mohs hardness is about 7, granite hardness is 8), but it is convenient in the manufacture of various materials.

Granite can be radioactive, because it may contain small amounts of uranium, radon gas. There are types of granites, the radiation of which is 20 times higher than the maximum allowable rate. You should not be afraid of this stone, since it can only be dangerous indoors (it can even provoke lung cancer), granite outdoors does not pose a significant danger to humans. Nowadays, black granite is being tested for radiation safety, which must be confirmed by a Certificate, which indicates that the level of radiation does not exceed the maximum allowable standards.

Application

Made from granite

• facing plates for finishing of facades, walls, floors;
• paving slabs and paving stones, in the western United States there is a type of granite "Pluto", paving stones around the White House in Washington are made of it;
• monuments, sculptures;
• various crafts for office tables;
• vases;
• window sills;
• steps for stairs;
• fences;
• it is possible to build a house made entirely of granite, but given the possible radioactivity of the stone, the construction of granite housing is a controversial decision.

Geography

Interesting facts about the geography of granite. The largest exporters are Italy, China, India.

The third highest peak in the world - Konchejunga (8450 meters) is almost completely covered with granite. Climbing this mountain is very difficult - according to statistics, about 22% of climbers die. The only woman who managed to climb this Himalayan peak was climber Jeanette Harrison, she managed to conquer Konchejunga in 1998. Everest consists of limestone, K2 is made of gneiss, it is easier to climb them (but it is still very difficult, there is also a high mortality rate on these mountains, according to statistics, about 7 percent of climbers die on Everest, on K2 - 23 percent of climbers).

Many high mountains are made of granite - the Mont Blanc alpine massif, the Bugabos Gorge, the Pine and Fitzroy massifs in Patagonia.

Mount Fitzroy in Patagonia

Rocks in the US states of Oregon, California, Colorado are formed from rhyolites, a volcanic analogue of granite. Rhyolites are distributed in all areas of the world where there was active volcanic activity. Mainly white rhyolites, shades depend on inclusions (quartz, plagioclase, sanidine, biotite, magnetite). Mainly white rhyolites, shades depend on inclusions (quartz, plagioclase, sanidine, biotite, magnetite).

In Ukraine, the banks of the Southern Bug River are made of granite. This river also has granite rapids. These rapids are the only ones in Central Europe that have been preserved in the form in which they existed for many thousands of years. The rapids in other areas are, as a rule, flooded by reservoirs. On the basis of granite rocks, a natural complex of the Granite-Steppe Bug area was formed, it is located in the northwestern part of the Nikolaev region. The granite-steppe coastal zone is considered one of the oldest land areas in Eurasia (it was not a seabed) over the past 60 million years. The natural complex includes the ecosystem of the Southern Bug River between the cities of Pervomaisk (the northern extreme point) and Yuzhnoukrainsk (the southern extreme point), as well as the ecosystems of the tributary of the Southern Bug - the Dead Waterway (Aktovsky Canyon), Arbuzino. There are villages Grushevka, Migiya, where there are Migiya rapids - one of the few rapids in Ukraine, where in the summer you can organize water slalom training and extreme water tourism. On the basis of granite outcrops on the Bug River, the Regional Landscape Park "Granite-Steppe Pobuzhie" was created.

In comparison with humanity, granite can indeed be considered eternal. The age of even the youngest granites is 2 million years, while the age of the Homo Sapiens species is measured in only tens of millennia. The oldest granites are billions of years old.

Geologists call granite the "calling card" of the planet Earth. Many other rocks are also found on other planets and their satellites that have a solid surface, but granite has not yet been found anywhere except the Earth. Meanwhile, all the planets of the solar system were formed from one gas and dust cloud. This makes the problem of the origin of granite especially puzzling.

Background

Geologists of the 18th century associated the origin of granite with the ancient ocean. They believed that crystals settled to the bottom from sea water, from which granite was formed. Scientists who hold such views are called Neptunists.

At the beginning of the 19th century, another theory appeared, the adherents of which were called plutonists. They believed that granite was generated by volcanic magma. These scientists imagined the process of granite formation as follows: hot aqueous solutions coming from the depths of the earth dissolve some of the chemical elements that make up the rocks. Their place is taken by other elements brought by aqueous solutions, and this is how granite is formed.

This view was also very far from the truth. But we should not forget that at that time scientists had little information about the composition of granite rocks, and the physicochemical processes occurring in the earth's crust were not entirely clear. And yet the direction was correct: the formation of granite is really associated with magma and volcanic activity.

Modern idea of ​​the origin of granite

The process of granite formation was explained by the American geologist N. Bowen. He connected the origin of this rock with the crystallization of basalt magma. This explains where granite could come from on Earth, if it is not found on other planets and satellites of the solar system, because there are basalt rocks there. Crystallization of minerals in basaltic magma proceeds in a certain sequence, which was called the "Bowen series". There is a gradual enrichment of the melt with various low-melting chemical elements - sodium, potassium,. Granite is the result of this process.

The magmatic origin of granite today can be considered proven. Even modern volcanic eruptions often bring to the surface magma close in composition to granite.

Granite rock is used in construction and decoration. The properties of this rock allow structures built with its use to withstand centuries. This material has been known since ancient times. Until our time, decor elements made of granite in distant medieval times have been preserved. As now, people at that distant time also wanted to build strong and durable houses and bridges. Despite the fact that granite has been known to man for quite a few centuries, it does not lose its popularity. In the modern world, there is a huge amount of new technologies, new materials, both natural and man-made. But at the same time, granite is not inferior to all these technologies, and it is still used in the construction of bridges, in the lining of embankments and pools. Of course, this is not the whole list. Due to its properties, granite is used in various conditions.

Basic properties of granite rock.

Long service life or durability. Fine-grained granite can withstand several hundred years, this is proved by structures that have survived from ancient times.

Strength. This material is resistant to abrasion, cracking, compression, abrasion, as well as acid and precipitation.

Waterproof. This stone practically does not absorb water, its water absorption is seventeen hundredths of a percent.

Environmental friendliness. Since it is a natural stone, its use cannot harm human health, such as artificially created materials, or materials using glue, the fumes of which are dangerous.

Rich texture. This is a unique property of granite. Its textures and drawings are unique, even similar ones are not found.

Granite is an amazing stone. In addition to excellent mechanical properties, it has amazing aesthetic properties.