sedimentary

Sandstone

Arenite (with iron oxide cement)

Hardness: 6-7 (Mohs scale); Color: Reddish-brown, tan, or rust; Luster: Dull/Earthy; Crystal structure: Clastic (sand grains); Cleavage: None; Specific Gravity: 2.2-2.8

Hardness: 6-7 (Mohs scale)
Color: Reddish-brown, tan, or rust
Luster: Dull/Earthy

Identified May 28, 2026More sedimentary →

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Physical properties

Hardness: 6-7 (Mohs scale); Color: Reddish-brown, tan, or rust; Luster: Dull/Earthy; Crystal structure: Clastic (sand grains); Cleavage: None; Specific Gravity: 2.2-2.8

Formation & geological history

Formed through the accumulation and cementation of sand-sized grains, typically quartz and feldspar, in environments like deserts, river deltas, or beaches. The reddish color indicates iron oxide (hematite) cementation.

Uses & applications

Used primarily as a building and paving material, in glass manufacturing (if high silica), and as a reservoir rock for oil and natural gas.

Geological facts

Sandstone makes up about 20-25% of all sedimentary rocks on Earth. The famous Red Rocks Amphitheatre in Colorado is made of this type of rock.

Field identification & locations

Identify by the 'sandpaper' feel of its surface. Common in arid regions and coastal cliffs. Collectors should look for unique layering (cross-bedding) or unusual shapes formed by wind erosion.