sedimentary
Sandstone (River Cobble)
Clastic Sandstone (SiO2 with accessory minerals)
Hardness: 6-7 (Mohs); Color: Tan, beige, or light brown; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.1-2.4
- Hardness
- 6-7 (Mohs)
- Color
- Tan, beige, or light brown
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Tan, beige, or light brown; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.1-2.4
Formation & geological history
Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments. This specific specimen shows high rounding and smoothing indicative of long-term transport by water (fluvial processes).
Uses & applications
Commonly used in construction as an aggregate, in landscaping, and sometimes as a decorative garden stone or 'river rock'.
Geological facts
Sandstone makes up about 10-25% of all sedimentary rocks on Earth. The smooth texture of this piece is a result of millions of micro-impacts with other rocks in a riverbed.
Field identification & locations
Identify by its gritty texture (like sandpaper) and visible sand grains. Found globally in riverbeds, glacial deposits, and ancient seabeds.
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Cone-in-cone structure (Secondary Sedimentary Structure)
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Sandstone Grain
Clastic Sedimentary Rock Grain (SiO2 dominated)
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Sandstone
Arenite (primarily SiO2)
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