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Granite is a rock formed in the depths of the Earth. When hot magma reaches the surface, a volcanic eruption begins. If the molten mass has not made its way up, a geological body of solidified magma is formed at depth. There are several varieties of deep rocks, one of them is granite.
Quartz
In granites, quartz is the hardest mineral; it is found very rarely in the form of crystals; it usually forms white, gray grains of irregular shape. Regular crystals form in voids (inside vein bodies).
Quartz crystals are shaped like hexagonal columns with a beveled top. Its colored varieties have their own names. Colorless crystals are called rock crystal, purple crystals of all shades are called amethyst, honey crystals are called citrine, smoky crystals are called rauchtopaz, black crystals are called morion.
Rice. 1. Intergrowth of amethyst crystals.
Experts grow artificial quartz, which is no different in properties from natural quartz.
In the Urals at the beginning of the twentieth century there was a mountain (Crystal Mountain), consisting of white dense quartz. Quartz mining began in the 1930s, and the quarry is still in operation.
Message about Granite
Granite is a mixture of minerals that mainly includes feldspar, but also mica and quartz. Its color depends on the composition and amount of minerals. Its density is 2600 kg/m3.
Granite is the main rock of the Earth, having an igneous composition along with basalt. Russia has granite reserves in Primorye, Transbaikalia, Khabarovsk Territory, Karelia and several other regions. Granite is distributed throughout the world and is mined in many countries. All types of granites are formed due to volcanic eruptions. Magma flowing into the earth's cavities crystallized, forming granite.
In ancient times, tombs were made of granite. In the Middle Ages it was used in the construction of large structures. Granite was mainly used for finishing streets and non-residential premises, as it contains carcinogenic gas. The engraved surface of granite conveys all the beauty of the stone. It is popular due to its durability and waterproofness. Granite contains approximately 50% oxygen. This stone keeps you cool in summer and warm in winter. Therefore, granite tolerates Russian weather well.
Granite takes part in the formation of continents and is considered the main element of the earth's crust. The most durable is fine-grained granite. This is the most durable and strong stone. Suppliers of this mineral are India, China and Italy. Houses and monuments are made from it; steps have recently become popular. Granite products always look rich.
Translated from Latin, granite means grain. The only thing in the world harder than granite is diamond. The color of granite depends on the type of feldspar, and can range from red to dark colors. There are white and gray granite. The tallest rocks in the world are granite. Kanchenjunga, which is located in the Himalayas, is considered the third highest mountain in the world. Its height is 8586 meters, that is, almost 9 kilometers. The mountain consists entirely of granite. The mineral is not afraid of heat and cold. Does not lose its properties for centuries. Contains uranium in small quantities, which can cause cancer. Black granite must be tested for radiation safety.
There are mainly three types of granite mining used. The first type is rock explosion, which is considered the cheapest method of extraction. The second is more gentle - using air. Extraction takes longer, but many monoliths are preserved without the slightest cracks, and there is very little production waste. The third method is considered the most modern and expensive, called the stone cutter method. It requires expensive equipment and specialist training. But the end result is a perfect, defect-free product.
Mica
The softest mineral in granite. It is observed in the form of thin plates of black or dark brown color. Some varieties of granite contain gray mica muscovite.
Mica crystals are thin-plate hexagonal columns. With a sharp knife you can split them into separate almost transparent plates.
Until the 13th century, there was no window glass yet; muscovite plates were used in rich houses. The binding was made of lead.
Rice. 2. Mica window.
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Use of granite and its minerals
Granite and its components are used in various industries.
Quartz is a raw material for the production of ordinary and fire-resistant glass, water filters, and is used in metallurgy, mechanical engineering, electrical engineering and electronics. In the form of natural crystals and faceted stones, it is inserted into jewelry.
Feldspar is necessary for the manufacture of ceramics, rubber products, toothpaste, and is needed in mechanical engineering and electrical engineering.
Mica is used in the production of paints and electrical insulation.
Solid blocks of granite serve as the basis for monuments, for example, the base of the “Bronze Horseman”. The cladding of subway walls, city stairs, building facades is polished granite slabs. Granite crushed stone is in demand for backfilling road bases.
Rice. 3. The Bronze Horseman.
What have we learned?
Granite is a deep-seated rock consisting of quartz, feldspar and mica. The components of granite are used in various fields: in the production of glass and ceramics, paints, rubber products, and for decorative works. A description of granite and its minerals can be included in a report for 2nd grade children for a lesson on the world around them.
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Cracks in granites
Granite massifs are often broken by cracks filled with quartz or calcite. Quartz contains minerals of iron, tungsten, and native gold. If the cracks are large and contain a lot of metals, they are developed as deposits.
Rice. 2. Quartz with gold.
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Geodynamic settings of granite 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 collision 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.
They are also formed in very small volumes in mid-ocean ridges, as evidenced by the presence of plagiogranites in ophiolite complexes.
Based on the content of dark-colored minerals, the following varieties are distinguished:
- hornblende
- biotite
- hornblende-biotite
- double mica
- mica
- hypersthene (charnockite)
- augite
- graphite
- diopside
- cordierite
- malacolithic
- pyroxene
- enstatite
- epidote
According to the varieties of potassium feldspar, the following varieties are distinguished:
- microcline
- orthoclase
The texture of granites is massive with very little porosity, characterized by a parallel arrangement of mineral components.
Based on the size of the grains that make up the mineral rock, three granite structures 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 greatly influence the construction properties of granite rocks: the smaller the grain sizes, the higher the strength characteristics and durability of the rocks.
These rocks are dense, durable, decorative, and easy to polish; have a wide range of colors from black to white.
Granite is characterized by a volumetric mass of 2.6-2.7 t/m3, porosity less than 1.5%. The compressive strength is 90-250 MPa and higher, and tensile, bending and shear strength is from 5 to 10% of this value.
Granite is a clearly crystalline, coarse-, medium-, or fine-grained massive igneous rock formed as a result of the slow cooling and solidification of magmatic melt at great depths.
Granite can also form during metamorphism, as a result of granitization processes of various rocks. Individual granite massifs are often attributed to either igneous, metamorphic, or even 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 grains have an irregular shape due to constrained growth during mass crystallization.
Mining locations
Granite is common on all continents of our planet. In the USA, the rock is found along the Atlantic coast, in the northern part of the country, the central part of the Ozark Plateau, and the Black Hills. The mineral is mainly mined in Vermont, Wisconsin, Georgia and South Dakota. In Europe, large volumes of the breed can be found in Germany, Italy, Spain, Portugal and the UK.
The stone is also common in Russia. Large granite deposits are located in the Urals, the Caucasus, the Far East, as well as in Eastern Siberia and the Karelo-Kola region. There are more than 50 deposits where piece stone is mined. Granite crushed stone and rubble can be found in regions such as Prionezhye, Ladoga, Karelian Isthmus, Primorye, Eastern Transbaikalia, Khabarovsk Territory. The material is also available in the Arkhangelsk, Voronezh, Sverdlovsk and Chelyabinsk regions. The mineral with a high degree of decorative value is found in the north-west of the country.
At least 200 granite deposits are known in the post-Soviet space. The largest mineral deposits are found in Ukraine (Zaporozhye and Poltava regions) and Belarus (Brest region).
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