Rocks. Classification.

The formations, consisting of minerals and arisen inside or on the surface of the earth under certain geological conditions, are called "rocks". They were formed more than 4600 million years ago and have a different structure and colors.

According to their origin, rocks are divided into three types: sedimentary, magmatic and metamorphic.

The first group of minerals is formed on the surface of the Earth's crust. Breeds of this species are formed as a result of accumulation of precipitation on land and in water bodies and their subsequent subsidence under the influence of gravity. Depending on the mode of education, they are divided into:

• Chemical rocks. This group of minerals is formed from aqueous solutions of nutrients, as well as from animal and plant remains accumulated at the bottom of the oceans, lakes and seas. This includes table salt and potassium salt deposited on the bottom of water bodies, silica found in hot springs, as well as combustible fossils (oil, gas, coal), phosphorites and limestones (shell rock, chalk, etc.). Many minerals of this group have a layered texture.

• Detrital. Are formed as a result of weathering or moving parts of rocks by wind, glacier or waters and their subsequent accumulation. As a result, they are even more crushed and crushed. Small, medium and coarse clastic rocks are found in size. Such minerals include pebbles, gravel, sand, gravel, clay.

Magmatic rocks arise as a result of the crystallization of molten matter located in the bowels of the Earth - magma. They account for more than 65% of the total volume of the earth's crust and are the most abundant minerals.

Magma is a silicate composition, saturated with gases and water vapor and melted to 1200 degrees. It comes to the surface of the earth solely under the influence of various geological factors, where, cooling, crystallizes and forms rocks, such as, for example, basalt, granite, olivine, pyroxenes, amphiboles.

Magmatic minerals are divided into intrusive and effusive.

• Intrusive rocks are located in the depths of the earth at a shallow depth. They differ in good crystallization and, depending on geometry and shape, are divided into batholiths (large ones), dikes (have a tubular structure and are formed as a result of filling cracks), veins (thin and long in length).
• Effusive formations occur when the magma flows out and consist of non-crystallized volcanic glass. Among the rocks of this type, there are huge basalt plateaus and lava flows.

Depending on the depth on which magma lies, there are three groups of igneous rocks:

• Plutonic - are formed in the lower part of the Earth's crust (partially or completely). Granite is one of such minerals.
• Volcanic - formed on the surface. This includes minerals like andesite.
• Hypabyssal - arise when magma is filled with cracks in already existing rocks. This group includes pegmatites.

Metamorphic rocks. This type of minerals is magmatic or sedimentary minerals, which, being in the bowels of the Earth, undergo significant transformation. Changes that occur as a result of a temperature drop, high pressure or chemical interactions cause the appearance of a new texture and structure of rocks, without affecting its chemical composition. As a result, one mineral without melting and dissolving is transformed into another, more solid and resistant. For example, limestone is transformed into marble, granite in gneiss, sandstone in quartz.

Thus, the rocks of metamorphic, sedimentary and magmatic origin collectively constitute the thickness of the earth's crust. These minerals are the main source of minerals used by man for material production.