sedimentary

Sandstone (River Cobble)

Sandstone (primarily composed of silica, SiO2)

AI-generated identification · may be incorrect

Hardness: 6-7 Mohs; Color: Tan to reddish-brown; Luster: Dull/Earthy; Crystal structure: Clastic/Granular; Cleavage: None; Specific Gravity: 2.2-2.8

Hardness: 6-7 Mohs
Color: Tan to reddish-brown
Luster: Dull/Earthy

Identified June 8, 2026More sedimentary →

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Physical properties

Hardness: 6-7 Mohs; Color: Tan to reddish-brown; Luster: Dull/Earthy; Crystal structure: Clastic/Granular; Cleavage: None; Specific Gravity: 2.2-2.8

Formation & geological history

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments over millions of years, often in riverbeds or coastal environments. This specific piece was further shaped into a smooth cobble by water erosion.

Uses & applications

Commonly used in construction, as a building material, and for sharpening tools. Smooth river stones are popular in landscaping and decorative aquariums.

Geological facts

Sandstone acts as a natural filter in nature and is one of the most common sedimentary rocks on Earth. Old Red Sandstone deposits are famous for preserving early vertebrate fossils.