Greywacke Zone

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The Schwarzphyllites originated from dark, clayey deposits in the deep sea. The dark, sometimes reddish color is due to oftenpresent organic components and iron compounds. However, none of the original clay minerals remain because the current mineral composition has formed through metamorphism (rock transformation) during a mountain-building process under extreme conditions (temperature ≈ 350°C - 550°C, pressure ≈ 200 - 1000 MPa).

Characteristic minerals now include mica, quartz, sometimes feldspar, chlorite, and iron oxide. The light layers were originally either sandy deposits or volcanic tuffs. The rocks are intensely schistose, often even multiple times, and folded. Despite the schistosity and metamorphism, the sedimentary structures are still recognizable.