Slate is what? Description and varieties of shale

Slate is a stone that is widely used in construction and decoration. A separate version of it is used in power engineering. What does he look like? What properties does it have?

Slate is ...

Slate is a rock, the minerals in which are located in layers, almost parallel to each other. It has a heterogeneous chemical composition, which can include minerals such as quartz, albite, chlorite, serpentine, feldspar, mica, graphite, etc.

The appearance of shales largely determines the amount and type of minerals that the rock includes, as well as the presence of various impurities. The shades of the stone range from yellow and brown to violet, red or gray.

The basis of the rocks are minerals of dark shades, so the most common in nature is the slate black, well, gray still. Stones of light shades are less common. As a rule, they have an attractive shine and are appreciated in ornamental works. The breed of black and gray colors does not shine, has a matte surface.

Slate is a stone whose age exceeds 400 million years. In the rock are often found the remains of fossil organisms. Slates belong to metamorphic rocks, that is, they were formed due to a change in the chemical-physical conditions - metamorphosis.

Varieties

There is a huge variety of shales. Their appearance and qualities are determined by deposits, mineralogical composition, formation conditions. They could form in the bowels of the planet with the participation of volcanic activity or on the seabed, where clay and other substances were pressed under the pressure of the mountains. The first are called orthoslants, the latter are called paraslants.

Slate is a collective name for rocks of excellent composition. They include the following types:

• Clayey;
• Aspidic;
• Crystalline;
• Carbonaceous;
• Chlorite;
• Combustible;
• Veldsky;
• Talcum and other.

Many characteristics of rocks depend on the depth at which they formed. At great depth, the pressure is stronger, and the temperature is higher. In such conditions, the rock acquires a crystalline structure. It has well-defined layers, which are easily divided into plates.

The layers can be slightly expressed and resemble crumpled folds. This occurs if the stones were formed with the aid of sedimentary rocks at a relatively shallow depth, and the pressure was directed toward the layers.

Crystal shales: photo and description

The rock has an increased schistosity, that is, it is easily crumbled and is divided into separate layers. The texture is usually well traced stripes, but sometimes it looks homogeneous. This type of shale has a granular-scaly or full-crystalline structure.

They contain a lot of mica and quartz. As additional minerals, the rock may include staurolite, graphite, garnet, calcite and andalusite. In composition, crystalline schists are divided into:

• Talcum powder;
• Mica;
• Amphibole.

Most often, their surface has a strong glassy sheen, rarely matte. The hardness of the rock is average - the blade leaves a shallow trail. The color of crystalline schists varies from dark to light, depending on the composition. Light shades give quartz, calcite, muscovite. Dark colors appear when biotite or graphite predominates.

Oil shale

One of the most fragile and light is oil shale. Their color can be brown, gray or yellowish brown. In wet form, the stones of gray color acquire a blue-black hue and resemble coal.

The main feature of the breed is the ability to ignite. Due to this, it is used as fuel instead of peat and coal. Most of all, shales of light shades are appreciated. In the 17th century, they learned how to extract tar, oil and tar from the combustion process.

The combustible, or pyrobituminous schists have a massive texture. They belong to sedimentary rocks, the basis of which is silicon or clay. In addition to minerals, the stone also contains organic substances, with which its combustible properties are related. 15-40% of the rock consists of decomposed organisms and algae.

Clay shale

This type of shale consists of minerals of clay origin, for example, chlorites. Layers in them are placed in parallel, and the texture resembles clay. They are located in the oldest geological sediments and make up more than half of the sedimentary rocks of the planet.

Quartz, spar or pyrite are often included as impurities in them. Sometimes the composition includes even oil impurities. The breed does not soak in the water. With a longer exposure to pressure and temperatures, it turns into phyllites or chlorite shales.

It is dominated by dark gray, black, greenish and reddish shades. Clay shales can be very hard (grinding shales), soft (slate, drawing) or loose (alum).

Deposits and applications

Shales are common in many parts of the earth. The largest deposits are in Russia, Australia, Turkey, Austria, England, USA, South Africa and China. The best quality oil shale is found in the Sydney basin of Australia and in the Baltic States. Crystalline mined in Ukraine, the Alps, in the area of the Baltic crystalline shield.

Slate is an excellent material for exterior decoration of buildings. It is widely used in construction and decoration. Some species of rock are used as fire-resistant raw materials. Fuchsite shales are semiprecious stones. They are suitable for the manufacture of decorative details, small sculptures, interior design.

A separate type of shale is used to produce graphite, quartz, garnet. Chloride species make paper. Other types are used for the production of varnishes, motor oils, cosmetics and perfumes. Some of them are used in medicine as a source of magnesium and silicon.