sedimentary
Sandstone (River Cobble)
Clastic sedimentary rock (primarily SiO2 with various lithic fragments)
Hardness: 6-7 on Mohs scale; Color: Tan, brownish-grey; Luster: Dull/Earthy; Crystal Structure: Granular/Clastic (sand-sized grains); Cleavage: None; Specific Gravity: 2.2-2.8
- Hardness
- 6-7 on Mohs scale
- Color
- Tan, brownish-grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Tan, brownish-grey; Luster: Dull/Earthy; Crystal Structure: Granular/Clastic (sand-sized grains); Cleavage: None; Specific Gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation, compaction, and cementation of mineral particles or rock fragments. This specific rounded specimen underwent mechanical weathering and transport in a high-energy fluvial (river) environment, likely during the Quaternary period.
Uses & applications
Commonly used as construction aggregate, road base, and decorative landscaping stone. High-quality sandstone is used in architecture and glass manufacturing.
Geological facts
Sandstone makes up about 20-25% of all sedimentary rocks on Earth. The rounded 'cobble' shape indicates it has traveled many miles from its original source, smoothed by the abrasive action of water and other rocks.
Field identification & locations
Identify by its gritty texture (feels like sandpaper) and visible sand grains. Found globally in riverbeds, beaches, and desert basins. For collectors, look for unique banding or fossil inclusions.
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