sedimentary

Sandstone (River Cobble)

Arenite

Hardness: 6-7 (Mohs); Color: Tan/Beige/Yellowish-brown; Luster: Dull/Earthy; Crystal Structure: Clastic; Cleavage: None; Specific Gravity: 2.2-2.8. Highly abrasive texture.

Hardness: 6-7 (Mohs)
Color: Tan/Beige/Yellowish-brown
Luster: Dull/Earthy

Identified April 19, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (Mohs); Color: Tan/Beige/Yellowish-brown; Luster: Dull/Earthy; Crystal Structure: Clastic; Cleavage: None; Specific Gravity: 2.2-2.8. Highly abrasive texture.

Formation & geological history

Formed from the accumulation and cementation of sand-sized grains, primarily quartz. This specific specimen has been rounded by fluvial processes (river erosion) over thousands of years.

Uses & applications

Commonly used in landscaping as decorative stone, construction aggregate, and historically for grinding tools or building materials.

Geological facts

Sandstone makes up about 20% of all sedimentary rocks on Earth. The smooth, oval shape is the result of 'saltation' where the rock bounces along a riverbed, wearing down its edges.

Field identification & locations

Identify by its gritty, sandpaper-like feel and visible small grains. Common in riverbeds, deltas, and landscaping mulch beds. To test, it should be able to scratch glass if it has high quartz content.