education, consisting of minerals and occurred in or on the earth's surface under certain geological conditions are called "rocks".They are formed 4.6 billion. Years ago and have a different structure and color.
In its origin rocks are divided into three types: sedimentary, igneous and metamorphic.
first group minerals formed on the surface of the Earth's crust.The rocks of this type are formed by the accumulation of sediments on land and in water bodies and their subsequent sedimentation by gravity.Depending on the method of education, they are divided into:
- Chemical rocks.This group of minerals is formed from aqueous solutions of nutrients, as well as remains of animals and plants that have accumulated at the bottom of oceans, lakes and seas.These include sodium and potassium salt, deposited on the bottom of ponds, silica, located in the hot springs, as well as fossil fuels (oil, gas, coal), phosphates and limestone (shell rock, chalk, etc.).Many of the minerals in this group have a layered texture.
- clastic.As a result of weathering or moving parts of the rocks by the wind, or a glacier waters and their subsequent accumulation.As a result, they are further crushed and milled.According to its size there are small, medium and coarse rock.These minerals include gravel, crushed stone, sand, gravel, clay.
Magmatic rocks are the result of the crystallization of the molten substance in the bowels of the earth - magma.They make up more than 65% of the Earth's crust and are the most common minerals.
Magma is a silicate composition, rich gases and water vapor and melted up to 1200 degrees.It comes to the surface only under the influence of various geological factors, which, cools, crystallizes and forms rocks, such as basalt, granite, olivine, pyroxene, amphibole.
igneous minerals are divided into intrusive and effusive.
- Intrusive rocks are placed in the ground at a shallow depth.They have good crystallization and, depending on the geometry and shape, subdivided into batholiths (have larger dimensions), dykes (have a tubular structure and are formed by filling cracks), the tubing (thin and long in length).
- effusive formation occur when the output magma out and neraskristallizovannogo consist of volcanic glass.Among the rocks of this type are allocated huge basalt lava plateaus and sinters.
depending on the depth at which lies the magma, there are three groups of igneous rocks:
- Plutonic - formed at the bottom of the Earth's crust (partially or completely).For this type of minerals is granite.
- volcanic - formed on the surface.These include minerals such as andesite.
- hypabyssal - occur when magma filling cracks in the existing rocks.This group can be attributed pegmatites.
metamorphic rocks.This type of mineral is an igneous or sedimentary minerals, which, being in the bowels of the Earth, are undergoing significant transformation.Changes as a result of changes in temperature, high pressure, or chemical reactions cause the appearance of a new texture and structure of rocks, without affecting its chemical composition.As a result, one mineral without melting and dissolution is converted into another, more solid and durable.For example, limestone is transformed into marble, granite gneiss in the sandstone into quartz.
Thus, metamorphic rocks, sedimentary and igneous origin together make up the earth's crust.These minerals are the main source of minerals, used by man for material production.
