Shales

The paragenesis of minerals depends not only on the chemical composition of the formed rocks, but also to a large extent on the depth at which the process occurs, i.e., on thermodynamic conditions. Under the influence of strong dynamic influences, the rocks turn into crystalline schists, retaining the ability to easily stratify or break into plates and tiles (these are, first of all, clay, slate and mica schists, as well as gneisses , etc.). If thin-layered sedimentary rocks are involved in the process of metamorphism, and the direction of pressure coincides with the direction of layering or close to it, then the layers are crushed with the formation of numerous small folds ^[1] . As a result, shales are characterized by shale - the ability to easily split into separate plates. Relate to terrigenous or metamorphic rocks . Like any morphological term, the concept of slate is collective in nature and can refer to folded rocks that are very different in terms of composition.

Some, for example, in the Zelenhofen shales (dense fine-grained rocks, presumably formed in sea lagoons ) usually contain many fossil remains .

Interesting observations about shale rocks in the East Sayan were left by Prince Kropotkin , who visited Buryatia in the middle of the 19th century . In particular, he drew attention to the species diversity of folded rocks in the Tunkinsky depression , in the place where once, according to his observations, there was a large lake. The water of this natural body of water once stood four meters above the current level of the Pearl , but then retreated, exposing the eroded rocks.

Since it was already late, and two more difficult crossings over the Pearls were ahead, I crossed to its right bank and barely got out among the dense forest, mud and mossy bumps to the mountains of the right bank, where I met only the outcrops of Jewish stone , stretching for half a half. In syenite comes across venice . Pearls roll their fast waves, wriggling along the plains and inflicting huge boulders of granites , Jewish stone with yellow sherl crystals, granular quartz , clad in black mica of gneiss and other crystalline schists.

- Peter Kropotkin , “A Trip to the Okinsky Guard” ^[2] ( Chapter II, “Tunkinskaya Depression ”)

In construction, it is used as an external finishing material, as well as the top layer of the roof ( slate ).

Fuchsite slate, according to the classification of A. E. Fersman and M. Bauer, refers to ornamental (semiprecious) stones of the second order ^[3] .

• Metamorphic rocks
• Oil shale
• Shale
• Schist
• Veld shales
• Crystal shales
• Coal shale
• Shale gas

• Filippov M.M. Nigozersky schists. - Petrozavodsk: KarRC RAS, 2007 .-- 469 p.

• Slates - article from the Great Soviet Encyclopedia