sedimentary
Sandstone (Greywacke)
Arenite/Greywacke (SiO2 major)
AI-generated identification · may be incorrectHardness: 6-7 Mohs; Color: Brownish-grey to tan; Luster: Dull/Earthy; Crystal structure: Clastic (granular); Cleavage: None; Specific gravity: 2.6-2.7
- Hardness
- 6-7 Mohs
- Color
- Brownish-grey to tan
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 Mohs; Color: Brownish-grey to tan; Luster: Dull/Earthy; Crystal structure: Clastic (granular); Cleavage: None; Specific gravity: 2.6-2.7
Formation & geological history
Formed from the accumulation of sand-sized mineral grains or rock fragments, cemented together by pressure and silica or calcite. This specimen shows significant rounding from river or coastal erosion.
Uses & applications
Common varieties are used in construction, road base, and landscaping. Smooth river stones like this are popular for decoration and stress-relief stones.
Geological facts
Sandstone preserves records of ancient environments, such as riverbeds or desert dunes. This specific rounded shape indicates the rock spent thousands of years being tumbled in water.
Field identification & locations
Identify by its gritty texture (feels like sandpaper) and visible grains. Commonly found in riverbeds, beaches, and sedimentary basins worldwide.
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