sedimentary
Sandstone (Greywacke)
Arenite / Clastic Sedimentary Rock
Hardness: 6-7 Mohs; Color: Grey to brownish-grey; Luster: Dull/Earthy; Structure: Fine-grained clastic texture with visible sand particles; Cleavage: None; Specific Gravity: 2.2-2.8.
- Hardness
- 6-7 Mohs
- Color
- Grey to brownish-grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 Mohs; Color: Grey to brownish-grey; Luster: Dull/Earthy; Structure: Fine-grained clastic texture with visible sand particles; Cleavage: None; Specific Gravity: 2.2-2.8.
Formation & geological history
Formed through the accumulation and lithification of sand-sized mineral particles or rock fragments. This specific specimen appears water-worn, likely shaped by river or coastal erosion over thousands of years.
Uses & applications
Commonly used in construction as aggregate, for paving, or as a decorative landscaping stone. Very fine-grained varieties can be used as whetstones for sharpening tools.
Geological facts
Greywacke is often called 'dirty sandstone' because it contains a mix of poorly sorted grains and a clay matrix. It is frequently associated with deep-marine environments or submarine fans.
Field identification & locations
Identify by its gritty texture (feels like sandpaper) and visible small mineral grains. It is extremely common in riverbeds and mountainous regions where ancient seabeds have been uplifted.
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