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slate

slate

SRI Petrography ID: 43

slate

Kieslinger Dekorgestein und Baugesteinsammlung
Mining district: Austria – Carinthia – Hermagor - Kötschach-Mauthen / Kreuzberg
GBA-ID.-No.: 2107, drawer-No: 156

Names

[de] Tonschiefer
[en] slate

Description

fine-grained (grains only visible in microscope), foliated metamorphic rock splits into characteristic, thin slices, very cleavable. Slate is formed when shale-type sedimentary rocks (clay, volcanic ash) are metamorphosed by high pressure, causing the flaky minerals like mica, clay and chlorite to be reoriented. Slate is characteristically grey or grey-blue in colour (but can also be coloured red, green or black) and intermediate in hardness between mica schists and shale.
Slate consists mainly of quartz and mica, sometimes pyrite and other minerals.

Color

Slate is characteristically grey or grey-blue in colour, but also black, purple, red or green varieties occur.

Grain Size

fine grained

Texture

foliated

Minerals

quartz, muscovite, illite, biotite, chlorite, hematite, pyrite

Occurences

occurs all over the world in metasedimentic bodies, esp. in Cornwall, Germany, Northern Italy, Galicia

Comments

Slate is much finer grained than schist

Classification

Class

METAMORPHIC ROCKS

Broader Terms

sedimentary protolith

Narrower Terms

Austria-slate

Czech Republic-slate

England-slate

Germany-slate