Slate is a stone that is widely used in construction and decoration. A separate variety of it is used in energy. What does he look like? What properties does it have?
Slate is ...
Slate is a rock whose minerals are arranged in layers almost parallel to each other. It has a diverse chemical composition, which may include minerals such as quartz, albite, chlorite, serpentine, feldspars, 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. Stone shades range from yellow and brown to purple, red or gray.
The basis of the rock is minerals of dark shades, so the most common in nature is black shale, well, gray also. Stones of light shades are less common. As a rule, they have an attractive shine and are appreciated in craftsmanship. The breed of black and gray colors does not shine, has a matte surface.
Slate is a stone whose age exceeds 400 million years. The breed often finds preserved remains of fossil organisms. Slates belong to metamorphic rocks, that is, they formed due to changes in chemical and physical conditions - metamorphoses.
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 compressed under pressure from the mountains. The former are called orthoslists, the latter - paraslists.
Slate is a collective name for rocks of excellent composition. They include the following types:
- clayey;
- aspid;
- crystalline;
- carbonaceous;
- chlorite;
- combustible;
- veld;
- talc, etc.
Many rock characteristics depend on the depth at which they are formed. At great depths, pressure is stronger and temperatures are higher. Under such conditions, the rock acquires a crystalline structure. It has well-defined layers that can easily be separated into plates.
Layers may be weak and resemble wrinkled folds. This happens if the stones were formed using sedimentary rocks at a relatively shallow depth, and the pressure was directed towards the layers.
Crystal shales: photos and description
The breed has increased shale, that is, it easily crumbles and is divided into separate layers. Stripes are usually well traced in the texture, but sometimes it looks uniform. 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, pomegranate, calcite and andalusite. The composition of crystalline schists is divided into:
Most often, their surface has a strong glass luster, rarely matte. The hardness of the rock is medium - the knife leaves shallow marks. The color of crystalline schists ranges from dark to light, depending on the composition. Light shades are given by quartz, calcite, muscovite. Dark colors appear when biotite or graphite predominates.
Oil shale
One of the most fragile and light are oil shales. Their color can be brown, gray or tan. When wet, the gray stones acquire a blue-black hue and resemble coal.
The main feature of the breed is its ability to ignite. Due to this, it is used as fuel instead of peat and coal. Shades of light shades are most valued. As far back as the 17th century, they learned to extract tar, oil and tar from the combustion process.
Combustible, or pyrobituminous shales have a massive texture. They belong to sedimentary rocks, the basis of which is silicon or clay. In addition to minerals, stone also contains organic substances, which is why its combustible properties are associated. 15-40% of the breed consists of decomposed organisms and algae.
Clay shales
This type of shale consists of clay minerals , such as chlorites. The layers in them are placed in parallel, and the texture resembles clay. They are located in the oldest geological deposits and make up more than half of the planet's sedimentary rocks.
Quartz, spar or pyrites are often contained as impurities in them. Sometimes even impurities of oil are included. The breed does not soak in water. With a longer exposure to pressure and temperature, it turns into phyllites or chlorite schists.
Dark gray, black, greenish and reddish shades prevail here. Clay shales can be very hard (sharpening slates), soft (slate, drawing) or loose (alum).
Deposits and applications
Slates are common in many parts of the Earth. The largest deposits are located in Russia, Australia, Turkey, Austria, England, USA, South Africa and China. The highest quality oil shales are in the Sydney Basin of Australia and in the Baltic. Crystalline is mined in Ukraine, the Alps, in the area of the Baltic Crystal Shield.
Slate is an excellent material for the exterior decoration of buildings. It is widely used in construction and decoration. Some types of rocks are used as flame retardant raw materials. Fuchsite schists are semiprecious stones. They are suitable for the manufacture of decorative details, small sculptures, interior decoration.
A separate type of shale is used to produce graphite, quartz, and garnet. From 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.