And the city, and the stone, and the shoes... And it seems that these words have nothing in common, but this is a deceptive statement. “I’m in Slantsy, I’m going for shale in Slantsy!” - exclaimed a resident of the city of the same name, walking to a hardware store in flip-flops. Well, if they know about the famous city in which shoes were made for the Soviet Union, not many have heard about the slate rocks.
Natural slate
History of the stone
The word slate is formed not from the verb to send, as can rightly be noted, but from lay, lay. In the old days, this is what they called schist... Schists are a metamorphic (altered) rock formed during the Ordovician period 500 million years ago, formed from dark-colored minerals, feldspar or quartz. The concept of metamorphism is the change under pressure and temperature of an existing rock in the depths of the earth's crust in an environment of gases and aqueous solutions due to volcanic and tectonic processes. Increasing temperature accelerates chemical reactions, promotes recrystallization, increases porosity and thus permeability to various minerals and fluids. The result is a rock that shimmers in the sun.
Varieties
There is a huge variety of slates. Their appearance and qualities are determined by deposits, mineralogical composition, and formation conditions. They could have formed in the bowels of the planet with the participation of volcanic activity or on the seabed, where clay and other substances were compressed under the pressure of the mountains. The former are called orthoschists, the latter - paraschists.
Slate is a collective name for rocks of different composition. They include the following types:
- clayey;
- slate;
- crystalline;
- carbonaceous;
- chlorite;
- flammable;
- veld;
- talc, etc.
Many characteristics of rocks depend on the depth at which they were formed. At greater depths, the pressure is stronger and the temperature is higher. Under such conditions, the rock acquires a crystalline structure. It has well-defined layers that are easily separated into plates.
The layers may be weakly expressed and resemble crumpled folds. This occurs if the stones were formed with the help of sedimentary rocks at a relatively shallow depth, and the pressure was directed towards the layers.
What does it look like
Natural slate is a rock with a schistose structure. According to the established rule, the name is given according to the rock-forming minerals according to the 1-2-3 scheme. The mineral that is the least abundant in a mineral and becomes the first in the name:
- chlorite – chlorite, epidote, quartz;
- garnet - garnet, quartz, feldspar.
In general, the color of the stone is varied, with pronounced shades, mainly depending on the host minerals. The most common are gray and black. The black color has a graphite tint with a matte sheen, while the gray one has an oily sheen predominates.
Black slate
Slate multicolor
Gray slate
Slate black graphite
Natural burgundy slate
Physical properties of shale by type
The physical properties of slate are very diverse, due to which it is widely used in various areas. The types of mineral are as follows:
- Roofing . The gray-black mineral is easy to split into thin layers. Samples are widely used for various technical tasks.
- Slate . Gray stone is soft and can split into rods.
- Grinding . Dirty yellow or green-gray natural stone is rich in silicon and iron. Characterized by a solid structure.
- Drawing . The black mineral is quite soft. It is rich in carbonaceous substances.
- Alum . The black stone with a porous structure contains a lot of sulfur pyrites.
Slates are easy to process and are used to create landscape, interior and other compositions.
Physico-chemical characteristics and varieties
More than 3 thousand mineral agglomerates are known in the world. For description and classification, a diagnostic technique based on physical, mechanical and chemical properties is used. This is necessary for an unambiguous identification of a particular mineral resource. Physical characteristics mean:
- optical:
- color;
— transparency;
- shine;
- mechanical:
— hardness;
- cleavage;
- special (the ability to deflect a magnetic needle, a characteristic garlic smell after rubbing, plasticity and others).
To further understand the concept of rock hardness, it is useful to become familiar with the Mohs scale, named after the 18th-19th century German mineralogist and geologist.
| Name of mineral | Appearance | Hardness | Machinability |
| Talc | 1 | Nail scratches remain | |
| Gypsum | 2 | Nail scratches remain | |
| Calcite | 3 | Traces of a copper coin remain | |
| Fluorite | 4 | Scratched by a steel nail or glass shard | |
| Apatite | 5 | Scratched by a steel nail or a piece of glass, but only with force | |
| Orthoclase | 6 | Mineral scratches glass, can be processed with a file | |
| Quartz | 7 | Processed with diamond, leaves scratches on glass | |
| Topaz | 8 | Processed with diamond, leaves scratches on glass | |
| Corundum | 9 | Processed with diamond, leaves scratches on glass | |
| Diamond | 10 | Cuts glass |
Let's consider the properties of slates, which have become widespread in industrial sectors, construction and decorative crafts.
- Clayey is a hard rock with a cryptocrystalline structure from gray to reddish in color with a matte sheen. It has a variety of shades and color saturation. Consists mainly of clay minerals, hardness 2-4 (slips on glass without leaving scratches). In rare cases, the presence of quartz may leave scratches. The presence of carbonate inclusions (calcite, marl, dolomite) is indicated by a chemical reaction with hydrochloric acid. The strength characteristics are significantly influenced by schistosity and cracks. The strength is low, it breaks easily along the schistose plane, varies from 20 MPa for talc and chlorite schists to 100-200 MPa for mica schists, however, for clayey schists the figure is less than 20 MPa. Almost all samples are anhydrous. According to the composition of minerals, they are divided into: – calcareous – contains calcite (5-22%), enters into a chemical reaction when exposed to hydrochloric acid; – siliceous-clayey – contains silica, is quite strong and hard; – roofing – capable of stratification into small-thick solid plates; – graphite – grayish, due to graphite crystals it leaves a line on the surface of the paper, dirtying your hands, tactilely greasy and soft; – bituminous – due to the presence of bitumen in the composition – black. When heated, a specific smell appears; – carbonaceous – black in color, draws on paper, but weakly. Hardness is low.
- Mica slate. It mainly contains various micas, hence the name. The color varies and is due to the micas contained in the rock. Includes sericite (thin scales), biotite, muscovite (light color). Forms a silky pearlescent sheen, sometimes silvery with a coarse-scale structure. The main difference from other types is the greater presence of mica relative to quartz. According to the composition of minerals it is divided into: – biotite (black shale); – muscovite (light); – double mica (same muscovite-biotite ratio); – mica-chlorite (difference from other varieties – the presence of chlorite, has a greenish color). – sericite is represented by sericite flakes, light gray in color with greenish inclusions. Clay mineralization is minimal. Hardness 3 (scratches plaster).
- The slate is nodular. Sometimes called mottled due to its texture and presence of mineral inclusions (spots). Color with a wide range, from dark gray to brown. Cryptocrystalline structure with mineral inclusions in the node zone. Pronounced mottled texture. Clay minerals interspersed in hematite and magnetite nodes are rock-forming. Stone samples react to a magnetic needle.
- Talc slate. It got its name because of its slate-like structure and the predominant presence of talc. A white, sometimes yellowish rock with a fine-grained structure, consisting of talc (greasy, leaves fingernail marks), quartz (scratches glass), and inclusions of calcite and chlorite (greenish color). Distinctive feature – soft, hardness on the scale – 2.
- Chlorite shale. It owes its name due to its schistosity and chlorite content. There is a beautiful green slate shimmering in the sun. With a cryptocrystalline structure, crystals of ore inclusions are often visible. Contains talc and chlorite and has a slightly greasy feel. Hardness value - 2.5. If there is more talc, then the shale is chlorite-talc, if there is mica, then it is chlorite-mica.
There are also oil shale, but we’ll talk about them a little later.
Crystal slates: photos and description
The rock has increased schistosity, that is, it easily crumbles and is divided into separate layers. The texture usually has good stripes, but sometimes it looks uniform. This type of shales has a granular-flaky or holocrystalline structure.
They contain a lot of mica and quartz. Additional minerals in the rock may include staurolite, graphite, garnet, calcite and andalusite. Based on their composition, crystalline schists are divided into:
- talc;
- mica;
- amphibole.
Most often, their surface has a strong glass sheen, rarely matte. The hardness of the rock is average - the knife leaves shallow marks. The color of crystalline schists ranges from dark to light depending on the composition. Light shades are produced by quartz, calcite, and muscovite. Dark colors appear when biotite or graphite predominates.
Places and methods of extraction
The main large deposits of shale minerals are located in Russia (Caucasus, Urals, Altai Territory), USA, Germany, France and Spain. Claystones are mined in quarries or mines in blocks. Then they are split into slabs of the required sizes for ease of transportation. Typically, blocks are formed according to dimensions (1-5 meters) and stacked in parallel layers. Large panels are rare. This is due to the intensity of the occurrence; waste sometimes accounts for up to 80% of the extracted raw materials. After the shale rock is separated, sorting occurs. The highest grade is formed from products with a thickness tolerance of no more than 1 mm. Thus, the pack contains a batch with a nominal value of 5 mm with a discrepancy in standard size of 4-6 mm. Quality requirements depend on mining conditions and vary from country to country. For America, resistance to weathering is important, but for the European continent, conditions for frost resistance are required. Each country is guided by its own criteria and standards. The most demanding quality standard in the world is French; in addition, all manufacturers undergo EU certification. Today, the problem of depletion of European quarries arises, so many suppliers purchase minerals from the Asian region. Such rock material is considered “young”. Through selection, this product is passed off as European. Cheap products are often offered instead of high-quality ones. Shale materials do not support the load, crack, have irregular geometry, and are sometimes radioactive. Laboratory testing is recommended before purchase. The main supplier in Europe today is Spain. The share of development and production of this state in the Old World is 90%. In Latin America, Brazil ranks first in the development of roofing slate. It is also in second place in the world in production after Spain. There are more than 100 quarries in Brazil, as well as 500 processing plants. There are also deposits in Russia, located in the Urals and North Ossetia. Unfortunately, our country is completely dependent on imports, and production and development is of a focal nature, often in small teams for specific needs. There is hope that the deposits of the Caucasus will be appreciated and will find their buyer.
Prevalence
Most types of slate are common throughout the world. But still not everything. So one of the most common is clay shale, which can be found in most countries of the world.
But chlorite shales are not very common, it is known for sure that their deposits exist:
- in the Ural Mountains and a number of other regions of Russia;
- in the state of Tyrol (Austria);
- in Australia;
- in several regions of England;
- Turkey;
- in South Africa and on the island of Madagascar;
- on the territory of China;
- in the United States of America.
Talc shales are widespread in the mountains and foothills of the Urals, in southern Siberia and other regions of Russia. In Ukraine, European countries (especially in the Alps), Brazil, the United States, etc.
Crystalline ones are also very widespread, they can be found in all areas designated as metamorphic. In particular, on the Ukrainian and Baltic shields and folded areas, for example, in the Alps. They can also be found on continental margins, for example on Sakhalin Island. This is just a small part of a long list that includes South Africa, Japan and America, etc.
By the way, an interesting fact: most of the famous Manhattan Island, which is part of the city of New York, consists of crystalline slate.
Magic properties
Since ancient times, people have endowed minerals with the power of magic. There is a belief that our wonderful stone also provides a subtle connection between man and the cosmos. Of course, this is not so easy to do the first time and right away, so there is a certain ritual. At midnight, when the Moon is full, light 2 candles, place a shale shard between them and gaze at it for half an hour. He himself will show all his strength. After some time, pictures and images of figures will appear. Ask him to interpret these visions, and he will do it. Only for this you need to put it under the pillow, after wrapping it in a silk scarf. The interpretation of what you see will happen in a dream.
Artificial slate
Decorative slate is the best solution for those who want to express their special uniqueness of original design in the interior decoration of their home. Artificial stone has excellent technical characteristics, is easy to process and is no different in appearance from natural stone. The manufacturing process occurs by mixing basalt chips with modern plasticizers, or from gypsum. Gypsum tiles with imitation brick or stone are used in dry rooms, as they strongly absorb water.
Decorative slate in the interior
The artificial product has a number of advantages:
- lighter weight compared to natural slate;
- use in any climatic conditions;
- ease of installation;
- less waste and formation of a cut without chipping;
- elasticity and durability.
Application of slate in various fields
Today, slate is often found in various industries, its use is very widespread. This is due not only to its physical, but also aesthetic properties. Stone can be called a universal material, as it is suitable for:
Interior design of houses and offices, facade finishing
Finishing slate is used for cladding the exterior of buildings. The stone can withstand changes in temperature and humidity. With its help, floors are installed in rooms for various purposes. Stone is also used for wall decoration. Slate is suitable for construction and cladding of fireplaces.
Landscape decoration
Flagstone such as slate cannot be called cheap, but this does not make it less popular for use in decorating local areas, gardens and parks. It has proven itself to be excellent for creating paths, steps, columns, fountains and more.
Gray slate has a characteristic oily sheen, which is due to the high granite content
Roofing arrangements
Slate in construction is often used for roofing various structures. The material is quite durable and has a low level of water absorption. The structure of the coating looks respectable for a long time, while the surface does not accumulate dust and dirt.
Black slate has a graphite tint and is used as a finishing material
Creation of designer dishes and souvenirs
The characteristics of slate were appreciated by craftsmen involved in the manufacture of tableware. The products are popular not only among restaurateurs, but also in everyday life. Unique products are comfortable and practical, they are shock-resistant and easy to clean.
You can learn more about the features and advantages of natural slate from specialists. Call us, our managers will select the optimal stone option based on your tasks!
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Price
Slate roofing tiles are expensive compared to traditional materials. The high cost is due to the difficulty of extracting and manually processing each element. Prices for slate roofing from Spain start from 3,500 rubles per 1 m2. Brazilian products are in the same price range. The German manufacturer offers a price range from 2850 to 9750 rubles per square meter. Prices for dishes made from this stone depend on the complexity of processing, the image of the author and the use of accompanying materials (valuable wood, glass). For example, a simple cutting board will cost 1 thousand rubles, a stone for finishing knives will cost 650 rubles.
Respect for one’s personality and a reverent attitude towards health should be demonstrated by every person. Products made from slate will complement life with stone tranquility, and the call of our ancestors will remind us of our roots.
