sedimentary

Red Sandstone

Arenite (primarily composed of SiO2 with Fe2O3 cement)

Hardness: 6-7 on Mohs scale; Color: Red, reddish-brown, or orange due to iron oxide; Luster: Dull/Earthy; Crystal structure: Clastic (granular); Cleavage: None (conchoidal fracture); Specific gravity: 2.2 to 2.8

Hardness: 6-7 on Mohs scale
Color: Red, reddish-brown, or orange due to iron oxide
Luster: Dull/Earthy

Identified March 30, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed from the accumulation of sand-sized mineral grains or rock fragments. The red color indicates formation in an oxygen-rich environment (arid or desert-like) where iron minerals oxidize. Most famous deposits date to the Devonian or Triassic periods.

Uses & applications

Extensively used in construction as a building material (brownstones), masonry, paving stones, and sometimes crushed for road base. In jewelry, it is occasionally used for beads or cabochons if it contains interesting patterns.

Geological facts

Many famous landmarks, such as the Grand Canyon in the USA and the Treasury at Petra in Jordan, are composed of red sandstone. It is often referred to as 'Old Red Sandstone' in European geological contexts.

Field identification & locations

Identify by its gritty, sandpaper-like texture and its tendency to rub off tiny grains of sand when scratched. Found worldwide in sedimentary basins, especially in the Western United States, Scotland, and Australia.

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