sedimentary

Sandstone (Pebble/Cobble)

Arenite (primarily SiO2)

Hardness: 6-7 on Mohs scale; Color: Tan, brown, or buff with grey inclusions; Luster: Dull/Earthy; Structure: Clastic (granular); Cleavage: None (conchoidal fracture on individual grains); Specific Gravity: 2.2-2.8

Hardness: 6-7 on Mohs scale
Color: Tan, brown, or buff with grey inclusions
Luster: Dull/Earthy

Identified March 29, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation and cementation of sand-sized mineral grains or rock fragments. This specimen shows significant rounding, indicating it was long-subjected to water erosion in a riverbed or coastal environment.

Uses & applications

Common sandstones are used in construction (as aggregate or dimension stone) and glass manufacturing. This specific water-worn cobble is primarily of interest for landscaping or river-rock decorative use.

Geological facts

Sandstone makes up about 20-25% of all sedimentary rocks on Earth. Because of its porosity, it is an important reservoir for groundwater and petroleum.

Field identification & locations

Identify in the field by its gritty 'sandpaper' texture and the presence of visible grains cemented together. This specimen found in a rounded state indicates it is a 'river rock'. Commonly found in sedimentary basins and along active or ancient waterways.

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