Slantsy

a city under oblast jurisdiction; administrative center of Slantsy Raion, Leningrad Oblast, RSFSR. Located on the Pliussa River, which empties into the Narva Reservoir. Railroad station on the Leningrad-Gdov line. Population, 42,700 (1975). Shale is mined and processed at Slantsy. The city has a cement plant, a brickyard, a regenerator plant, a combine for the production of construction components, a lumber combine, and other enterprises. It also has an industrial technicum. The general technical department of the Leningrad Institute of Mines is located in Slantsy.

a Russian term meaning rocks characterized by an almost parallel arrangement of elongated or platy materials and capable of splitting into thin sheets. The term covers the variety of laminated to foliated rocks encompassed by the three terms “shale,” “slate,” and “schist” in English. According to the degree of regional metamorphism, a distinction is made between two large groups of slantsy: (1) shales (including slates), which are weakly metamorphosed rocks; and (2) schists, which are extensively metamorphosed rocks.

Shales consist primarily of clay minerals, hydromicas, or, less frequently, montmorillonite. In the group of schists, various kinds of mica schists are distinguished—biotite, muscovite, and, less frequently, paragonite schists—according to the mineral composition; the minerals include micas, amphiboles, feldspars, and quartz. As the content of feldspars and quartz increases, the mica schists grade into gneisses, and the amphibo-lite schists grade into amphibolites. Schists sometimes bear the name of a relatively rare mineral that is included in their composition; examples are garnet, staurolite, and cyanite schists.

An intermediate position between the shales (and slates) and the schists is occupied by phyllites, chlorite schists, and green-schists. Such rocks have been subjected to metamorphism under the conditions of the greenschist facies at relatively shallow depths. In the composition of these rocks there are found micas and many green-colored minerals, such as chlorite, epidote, and various amphiboles. Greenschists are formed from sedimentary and igneous rocks.

Shales that have complete foliation are used as roofing slate. Roofing slate is extracted by quarrying and underground mining. The blocks of slate are cut and split into sheets about 0.5–1 cm thick, which are used for the roofing and facing of buildings.

Shales lacking complete foliation and the waste material from the production of roofing slates are used to make inflated shales. In the USSR, schungites, which are shales mined near the village of Shun’ga in Karelia, are used for these purposes. In inflated form, this material is known as schungisite and is used as a high-quality filler for concrete.

Schists, especially those similar to gneisses, are used as a construction material and as a source of refractory materials.

Shales rich in organic matter are used as combustible shales.