Granite is the most magmatic intrusive rock in the continental crust. The name of this excellent natural material is due to its porous-granular structure (from the Latin granum - "grain"). Granite is attributed to acid rocks due to the fact that it contains a large amount of silicon dioxide - SiO2. In addition to this element, granite contains alkali, as well as magnesium, iron and calcium. This rock is considered to be one of the most durable, hard and durable, its density is 2600 kg per cubic meter. In this article we will consider the composition of granite, and also tell about existing classifications of this rock, we will reveal its properties and features.
Origin and location of granite
It is believed that granites formed over a long period of geological history of all continents. There are two versions of the breed in question. The first says that granite is formed as a result of the process of crystallization of magmatic melt. According to the second theory, the stone considered by us was formed under the influence of ultrametamorphism. Under the influence of pressure, high temperatures and fluids rising from the deep seams of the earth, the process of granitization is carried out. A large number of deposits of this heavy-duty rock are known, including in the USA, China, Brazil, Scandinavia and Ukraine. In our country there are also rich deposits of this natural material. It is mined in fifty granite quarries, including in the Arkhangelsk and Voronezh regions, as well as in the Caucasus. Often, alongside the mentioned deposits, various ores are found, including tin, copper, zinc, tungsten, molybdenum and lead.
Consider what is included in the composition of granite. Feldspar and quartz
By its constituents, this rock belongs to the polymineral, that is, consisting not of one component, but of several. One of the main elements that make up the granite is feldspar. It is a mineral of the silicate group. As a rule, in granite it is not less than 50%, or even all 60! This rock-forming mineral is present in the rock in the form of potassium feldspar (orthoclase, adular) and acid plagioclase (oligoclase, bitovnita, Labrador, etc.). Another important component of granite is quartz - a very hard rock-forming mineral of the vast majority of igneous rocks. His share is not more than 30% of the total volume of the breed in question. The impregnations of it look like small vitreous grains. In the natural state, quartz is colorless, and as a rock in the granite composition acquires a different coloration - yellow, pink, red, purple, etc.
Dark-colored minerals and other inclusions in the composition of granite
In addition to quartz and feldspar, there are other inclusions in this acidic rock. Usually they occupy no more than 10% of the total. This biotite, lithium mica, muscovite and hornblende. A minor share is occupied by accessories - for example, apatite and zircon and alkaline minerals - tourmaline, pomegranate and topaz. So, we examined the composition of granite. The diagram clearly shows the main components of this natural material.
Types of granite
Depending on the characteristics of the mineral and chemical composition of granite, some of its varieties are distinguished. One way of ranking is built on the percentage of plagioclase in the rock. There are the following types of granite:
- Alkaline feldspar (less than 10% plagioclase);
- Granite proper (from 10% to 65% of plagioclase);
- Granodiorite (from 65% to 90% of plagioclase);
- Tonalite (over 90% of plagioclase).
In addition to the percentage of feldspar, the content of secondary dark-colored minerals is taken as a basis for distinguishing the types of the stone in question. According to this classification, such varieties of rock are distinguished: alaskite - granite, which does not include dark-colored metals, and leucogranite - which has a low content. Two-mica granite - consists, in addition to feldspar and quartz, from muscovite and biotite, and alkaline contains also aegirine and amphiboles.
Structural features of the rock
There is another classification, based on the structural and texture features of the mentioned rock. Advantageously, the granite has a granular-crystalline structure, but sometimes it is also porphyry-like. In the natural environment, the material is located in massive layers, formed as a result of magma cooling. In connection with the fact that it freezes unevenly, granite is formed, having a different structure, including fine and coarse-grained. Samples of the latter are called granite-porphyries. An example of a porphyritic rock with a coarse-grained structure can be granite-rapakivi (Finland). It has inclusions of an orthoclase the size of a chicken egg.
Granite painting
Minerals that are part of the granite, can paint this rock in different colors. As a rule, it is the orthoclase that determines the color of the stone. The most common is a light gray color. In Russia, the material of red color is widely distributed. In the mineral composition of granite with such a bright color includes feldspar, which has hematite crystals, otherwise - iron oxide. They give the rock a blood-red shade. Also come across stones of yellow, blue and pink colors. The emerald shade of the breed is obtained from green potassium feldspar - amazonite. Sometimes find granite unusual rainbow colors. It appears due to feldspar, which possesses irisation. Often it is the oligoclase and labrador that give a beautiful iridescent flicker, especially noticeable when turning the stone. This is an interesting material, granite.
Composition and properties of rock
This natural material has many remarkable properties, making it indispensable in many areas, especially in the construction sector. First, granite is durable. It can serve for a long time, preserving its original appearance. Sometimes it is called the "eternal stone" among the people, but all because nothing has happened to it for centuries. Secondly, this material is extremely durable. Products made of it are not subject to wear. Quartz - a mineral in the composition of granite - makes this rock so strong that when processing, grinding and cutting it uses saws with a special diamond coating. Thirdly, one of the most important properties of granite is its resistance to any external environment, as well as to acids. It does not require treatment and protection from a variety of oxidative and physical effects. Only at temperatures above 600 degrees can it change its structure and crack. Fourthly, the granite is resistant to moisture, it is practically waterproof, does not absorb water and is not destroyed due to precipitation. For centuries, buildings and monuments from granite can retain their original appearance. And, finally, it is important that granite is environmentally friendly. It is completely safe for humans. All these properties make the considered rock a valuable building material.
Application of granite
This stone is widely used for building and facing works, because it is longevous, resistant to environmental influences and special durability. Due to its resistance to friction and compression, it is often used in exterior and interior decoration of premises. Granite has a high resistance to pollution, so it is often used in the manufacture of handrails, stairs, columns, countertops, window sills and bar counters. Often, granite slabs are decorated with fireplaces and fountains, because it is resistant to temperature changes, and to absorption of moisture. In the exterior, this rock is often used as facing, masonry or building material. Laying pavements, roads and bridges, often piers, embankments and streets. Made of granite fences, supporting walls, they are decorated with facades and walls of buildings. And for this, a variety of colors can be used. In Russia the most commonly used are gray, white, red and brown varieties. Unfortunately, mining and processing of igneous rocks is difficult and expensive, so this material is rarely used for the construction of conventional buildings. In general, it is used to decorate objects that have a serious architectural value.
Monuments of architecture from a granite
After the correct grinding, the surface of the granite becomes mirror, while simultaneously reflecting and absorbing the light rays. Therefore, the stone looks very rich and effective, which makes it possible to use it for making monumental sculptures and architectural compositions. An example of beauty, elegance and durability of granite can be monuments of architecture, historical buildings and structures erected in many countries, including Russia. Any granite structure is remarkable for its majesty and monumentality, striking the imagination with its power and beauty.