Poorly sorted, dark sandstone with abundant rock fragments and clay matrix. Characteristic of turbidite sequences. Texture: Poorly sorted, angular grains. Rock type: Sedimentary Clastic. Grain size: Sand with clay matrix. Minerals present: Quartz, Feldspar, Rock fragments, Clay matrix. Formation: Deposited by turbidity currents in deep marine environments, creating graded beds in submarine fans. Common geological settings: Found in ancient turbidite sequences; Archean and Proterozoic greenstone belts. Common look-alikes and related entries: Sandstone, Siltstone, Phyllite.
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Last updated
2026-03-30T14:38:19.941535+00:00
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Rocks — U.S. National Park Service. Authoritative overview of rock groups, the rock cycle, and geologic processes.
Poorly sorted, dark sandstone with abundant rock fragments and clay matrix. Characteristic of turbidite sequences.
How can you identify Greywacke?
Compare several properties rather than relying on colour alone. This entry records rock type: Sedimentary Clastic; texture: Poorly sorted, angular grains; grain size: Sand with clay matrix; common minerals: Quartz, Feldspar, Rock fragments, Clay matrix. Confirm an important identification with additional field tests or qualified laboratory work.
How does Greywacke form?
Deposited by turbidity currents in deep marine environments, creating graded beds in submarine fans.
Where is Greywacke commonly found?
Found in ancient turbidite sequences; Archean and Proterozoic greenstone belts.
What is Greywacke commonly confused with?
Greywacke may be confused with Sandstone, Siltstone, Phyllite. Compare multiple diagnostic properties because colour and surface appearance can overlap.
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