Rock: species of rocks. Rock breeds by origin. Types of rocks

For many centuries the main building material was rock. Kinds of rocks were chosen by people depending on their characteristics, physical properties, strength, density, wear, etc. Since it is not so easy to manually work the stone, in ancient times only the most important objects were erected from it, for example, palaces, defensive Structures, cultural monuments. It is from such natural materials that the legendary Egyptian pyramids, the Great Wall of China, the Aztec pyramid, the Taj Mahal and other famous buildings that are wonders of the world are built.

Characteristic

Different stones are not a random accumulation of minerals, but their natural association. The definition of rocks can be formulated as follows: aggregates of minerals of natural origin with a constant structure and composition. For the first time this term was used by the Russian chemist and mineralogist VM Severgin in 1798. Depending on strength, decorativeness, density, porosity, frost resistance and other characteristics, minerals find different applications. Basically, in construction work, rocks are used.

Classification of rocks

Depending on the method of their formation, all the minerals can be divided into three large groups. Scientists distinguish sedimentary, magmatic and metamorphic rocks, a mantle type is assigned to a particular class. These are regular associations of various substances and minerals, of which a significant part of the earth's crust consists .

For many centuries volcanic emissions are caking and accumulating, magma cools and solidifies. Thus, magmatic rocks formed in the upper mantle and in the earth's crust at various depths are formed.

Flinders of various origins form a sedimentary type. Experts, through analysis, determine the type of environment in which materials were deposited, the features of their origin, the type of agents that carried them, and so on.

Metamorphic rocks appear when the magmatic and sedimentary species change in the thickness of the earth's crust. Such stones have their own unique chemical composition, but the basis is the maternal mineral from which they were formed. All metamorphic processes mainly occur in the depths of the earth's crust.

There are also mantle rocks, which were originally of magmatic origin, but then underwent significant changes in the mantle.

Magmatic rocks

Researchers distinguish two main types of magmatism: effusive and intrusive. They differ in the place of solidification of magma, as well as in the nature of its movement. In addition to these two, there are also vein and hypabyssal igneous rocks, which are intermediate types. They give dikes and veins, forming in the cracks of other stones when the magma solidifies.

Intrusive, or plutonic rocks undergo a long process of education, which can last more than a millennium. They can contain crystals of enormous size, since magma very slowly cools down at great depth. Although plutonic rocks are originally located in the depths of the earth's crust, when it is weathering and elevated, they very often transform into mountain massifs. A vivid example is Mount Spitskoppe in Namibia. The main minerals of this type are granite, labradorite, syenite, gabbro.

Magmatic rocks of effusive (volcanic) type are formed during the eruption of the volcano, that is, when magma emerges on the earth's surface. They do not create large crystals due to accelerated cooling. A clear example of a rock of this type are rhyolites and basalts. Of these, in antiquity often made various sculptures, monuments.

Sedimentary minerals

Clastic, chemogenic and organogenic are the main sedimentary types of rocks. They differ depending on the mode of origin and are formed on the earth's surface. The detrital type is formed due to cementation and caking of individual fragments of various rocks. A vivid example of such minerals can serve as sandstones and conglomerates. In Barcelona there is an array of Montserrat, here it is just a conglomerate, because it consists of cemented cobblestones clamped together with limestone.

Chemogenic types of rocks are formed from mineral particles precipitated in the water. It is on the basis of the mineral composition is the classification of stones. The most common representative of chemogen is limestone. For example, in Australia there is the Pinakli Desert, formed just from this breed. Organogenic type is similar in many respects to coal, because it is also formed due to caking of the remains of animals and plants. All sedimentary rocks are characterized by fracturing, porosity and solubility in water.

Metamorphic minerals

Classes of rocks are very often rather conventional. Metamorphic type can belong to minerals of both sedimentary and magmatic origin. They have varying degrees of intensity of transformation processes. If it is low, then metamorphism allows us to determine the parent rock, but with a high degree, it is simply impossible to do this. Such minerals change their composition and texture. For this reason, the metamorphic rocks are divided into shale and not shale, and, depending on the formation conditions, three large groups are distinguished: regional, hydrothermal and contact metamorphism.

Sometimes it happens that huge stone boulders are exposed from the outside, for example, low or high temperatures, pressure. A vivid example can serve as gneiss. These minerals can be considered regional. Hydrothermal metamorphism occurs with the participation of thermal springs. Minerals contact the ion-rich hot fluid that makes its way through the cracks of the mountains, with a chemical reaction that changes the composition of the rocks. An example is quartzite, often formed by limestones. There is also a contact metamorphism. In this case, the rocks are chemically affected and the temperature is increased by intrusive magmatic masses.

Properties of rocks

There are several properties of minerals, and they are all important to one degree or another. If they are used as a lining material, first of all attention is drawn to their aesthetic appeal. In some cases, the decorative quality of the stone is very important, its pattern, color is selected. The density index depends on how much the rock weighs. Kinds of rocks are easy and heavy. At the first density indicator - up to 2200 kg / m ³ , and in the second - more than 2200 kg / m ³ . If a stone is chosen for the construction of a structure, then its weight should be taken into account, the denser it is, the heavier the design will be. This parameter depends on the rock composition, porosity.

One of the most important properties of a stone (especially when it comes to construction) is strength. It depends on the wear resistance of the material. The stronger the mineral, the longer it will retain its original appearance. In this regard, all the stones are divided into three groups: low, medium strength and strong. It all depends on the composition of the rock, namely the hardness of the minerals. Among the strong stones are gabbro, granite, quartzite, limestone, marble, travertine to the middle, low tuffs, loose limestones.

Different types of rocks have different degrees of porosity. From this characteristic depends the acid and salt resistance, water absorption of the stone. On porosity, special attention should be paid in the event that a particular rock is selected as a liner. This indicator determines the durability of the material, its polishability, strength, decorativeness, thermal conductivity, machinability, etc. The higher the porosity, the less the weight of the stone, it is better processed, but at the same time its volume, strength decreases, and the polishability deteriorates.

The water absorption index of the rock is also very important. Depends frost, acid and salt resistance of the material. The water that gets into the pores, when frozen, increases in volume, creates pressure, which causes cracks in the end. The same thing happens with salt solutions, which promote the growth of crystals that create additional pressure. If the porosity of the mineral is low, then cracks appear in it, in some cases it may even crack. In porous stones, the pressure is evenly distributed, and no cracks appear.

The process of changing rocks is largely influenced by their acid resistance. Acids can convert and even destroy some minerals. Therefore, when choosing a stone for the erection of structures, this fact must also be taken into account. For example, hydrochloric acid is a serious threat to marble, dolomite, travertine. But limestone and granite are characterized by excellent acid resistance, so until today there are so many religious designs from these materials.

Conversion Processes

Huge boulders, majestic mountain ranges give the impression of mighty giants, over which time and various factors from outside do not dominate. It seems that they retain their original appearance for centuries and millennia, but this is not so. Over time, any rocks undergo substantial changes. Classification of rocks can determine how long the minerals retain their original shape, what exactly has the greatest impact on them.

The composition of the stone changes over a long period. The transformation of rocks can be of a natural or anthropogenic nature. The condition of the stones is influenced by factors such as thawed or underground water, rain, wind, sun, high and low temperatures. The destruction of rocks in a natural way is very slow, but it can not be stopped. Rain and wind wash and weather both the upper layers and underground landscapes. Gradually they change not only the form, but also the composition of minerals.

Anthropogenic processes are associated with human activities. Destruction of rocks can be carried out with the help of technology. For example, repeatedly construction brigades cleared the territory for the erection of structures, while removing part of the mountain massifs. Of course, such activities destroy the natural landscape and have a negative impact on it. Damaged rocks give cracks, because of this, caves and collapses occur. A person can change the appearance of minerals much faster than natural factors.

Thus, absolutely all mountainous terrains change their appearance with time. The speed of their transformation depends largely on the external conditions, the composition of the rock, the strength, the degree and duration of the impact. The process of transformation is also influenced by the climate of the terrain in which the stones are located.

Cycle of rocks

Geological processes of formation of magmatic, sedimentary and metamorphic minerals are tied in a certain cycle. It all starts with the fact that magma pours out, gradually cools and freezes, and magmatic rocks form. Kinds of rocks change as soon as they are on the earth's surface. Wind, water, temperature changes form a sedimentary type of minerals. The stones are crushed, weathered, transported from place to place, stopping in sedimentary basins. It is there that fragments of rocks complete their path, cake and become a sedimentary type of minerals. Over time, mountain massifs are submerged to a great depth, under the influence of tectonic processes. All this leads to the formation of metamorphic rocks. At high temperature and high pressure, the minerals melt, turning into magma. Over time, it freezes, forming a magmatic rock, and the process of forming stones begins from the beginning.

Petrology and Petrography

Both at the micro- and macro-level, mineral studies are being carried out. In the first case, only small particles of certain rocks are studied, their transparent and semitransparent spili. This allows you to establish the characteristics and properties of minerals. In the second case, scientists consider all the rocks in the aggregate, because they form a certain element of the earth's crust. Researchers manage to determine the history, features and approximate date of their formation.

The origin of rocks is studied in two disciplines: petrology and petrography. The first science examines the chemical and mineralogical composition of the stones, the conditions for their occurrence, texture and structure. Petrology also defines geological formations that make up the bulk of the earth's crust. Petrography is engaged in the classification and description of various breeds, this is more descriptive science. She studies individual samples of stones, their structure and composition. Petrographs work with transparent and semitransparent sections, using the microscope to examine the properties of their components. Also scientists can work with samples of rocks of impressive sizes.

There are several levels of study of minerals. First, scientists are engaged in the compilation of geological maps, followed by field, petrographic and geochemical surveys. They all complement each other and allow you to make a complete picture. Field studies allow us to determine the structural features, the position of the minerals, and establish the approximate time frames for their occurrence. Petrographic works determine what rocks exist by origin, what is the percentage ratio of minerals in them.

Petrology is a more complicated science. The need for special and deeper research arose as a result of the accumulation of a huge baggage of knowledge. To rocks are different types of minerals, which correspond to sedimentary, magmatic and metamorphic type. And each of them is the subject of study of a certain branch of the said discipline. So, the science of sedimentary minerals is interested in the texture and composition of salts, limestones, sandstones, conglomerates and other sedimentary rocks. Magmatic petrology considers minerals crystallized from molten magma. Metamorphic science studies marble, slates, gneisses and other rocks formed during the transformation.

Among other things, scientists are also engaged in geochemical research. They give a general idea of the chemical composition of the rock, its age, its place of origin, the mineral phases, the temperature and pressure at which it was formed.

The most common rocks

On our planet there is a huge amount of deposits of various minerals. Most of them people have found practical application. Some breeds are more in demand, some less. Let's talk about the stones most often used by man.

Granites

Perhaps, this is the most common stone, consisting of quartz, feldspar, mica. Granite has a granular-crystalline structure, divided into three categories: fine, medium and coarse-grained. The stone has a variety of shades, the rarest are blue-green, light gray and burgundy. Granite is highly polishable, some of its varieties are subjected to heat treatment. This is done to create additional decorative effects. Operational properties and mechanical characteristics of granite are estimated very high, so the stone is used for facing facades of structures, embankments, in the construction of basement structures. The stone is also used to create sculptures.

Sandstones

Another popular rock. Types of rocks depend on the mode of formation. Sandstones refer to the sedimentary type, because they consist of cemented sand. In nature there are stones of different colors: green, yellow, gray, red, brown. For decorative purposes, fine-grained brown, red and green sandstones are most often used. Mostly they go to the facing of buildings.

Marble

Belongs to a grainy-crystalline rock, appeared as a result of exposure to dolomite and limestone of high temperature and pressure. Marble has high decorative properties, it is easy to process. So, grinding minimizes clarity and brightness, polishing, on the contrary, enhances the pattern, cleavage brightens the background. The stone can be colored, gray and white.

Slate

The stone was formed because of strong compaction of clay, recrystallized under one-sided strong pressure. Slates are able to split into very thin plates, in color there are red and gray-brown, dark gray, black specimens. This decorative and durable material, which does not require any processing, is used for interior and exterior cladding.

Semiprecious stones

Such rocks as malachite, onyx, lapis lazuli, opal and jasper are valued more than others because they are less common in nature. These stones are used to make jewelry, decorative figures, small elements of the interior.