sedimentary

Sandstone

Arenite (primarily SiO2)

Hardness: 6-7 on Mohs scale (depending on cementation); Color: Tan, brown, or reddish-brown; Luster: Dull/Earthy; Structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.2-2.8

Hardness: 6-7 on Mohs scale (depending on cementation)
Color: Tan, brown, or reddish-brown
Luster: Dull/Earthy

Identified February 5, 2026More sedimentary →

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Physical properties

Hardness: 6-7 on Mohs scale (depending on cementation); Color: Tan, brown, or reddish-brown; Luster: Dull/Earthy; Structure: Granular/Clastic; Cleavage: None; Specific Gravity: 2.2-2.8

Formation & geological history

Formed through the accumulation and cementation of sand-sized silicate grains (mostly quartz). This specimen appears to be a water-worn river pebble, shaped by fluvial erosion over thousands of years.

Uses & applications

Commonly used as a building material, for paving stones, and in the production of glass (if high silica content). Small rounded pebbles are used in landscaping and aquariums.

Geological facts

Sandstone makes up about 20-25% of all sedimentary rocks on Earth. The red and brown hues are typically caused by iron oxide (rust) acting as a cementing agent between the sand grains.

Field identification & locations

Identify in the field by its gritty, sandpaper-like texture and visible sand grains. This water-rounded shape is common in riverbeds, beaches, and glacial till deposits.