sedimentary
Graywacke
Lithic Sandstone (Graywacke)
AI-generated identification · may be incorrectHardness: 6-7 on Mohs scale; Color: Dark gray to greenish-gray; Luster: Dull/Earthy; Structure: Fine-to-medium grained matrix with angular fragments; Cleavage: None (conchoidal fracture).
- Hardness
- 6-7 on Mohs scale
- Color
- Dark gray to greenish-gray
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Dark gray to greenish-gray; Luster: Dull/Earthy; Structure: Fine-to-medium grained matrix with angular fragments; Cleavage: None (conchoidal fracture).
Formation & geological history
Formed in deep-sea environments through turbidity currents (underwater landslides) that deposit poorly sorted sediment. Typically found in paleozoic or mesozoic deep-marine basins.
Uses & applications
Primarily used as construction aggregate, road base, and railroad ballast due to its hardness and durability.
Geological facts
Graywacke is often called 'dirty sandstone' because it contains a large amount of clay and silt along with sand-sized quartz and feldspar grains.
Field identification & locations
Identify by its characteristic 'salt and pepper' look under a lens, its extreme hardness, and lack of distinct bedding layers compared to other sandstones. Ubiquitous in orogenic belts.
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