sedimentary

Red Sandstone

Arenite (Ferruginous Sandstone)

Hardness: 6-7 (on Mohs scale); Color: Red, pink, or brownish-red due to iron oxide (hematite); Luster: Dull or earthy; Crystal structure: Clastic (granular texture); Cleavage: None; Specific gravity: 2.2-2.8

Hardness: 6-7 (on Mohs scale)
Color: Red, pink, or brownish-red due to iron oxide (hematite)
Luster: Dull or earthy

Identified June 2, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed by the accumulation and lithification of sand-sized mineral particles or rock fragments. The red color suggests deposition in an oxygen-rich terrestrial environment where iron minerals oxidized. Commonly associated with ancient river deltas, desserts, or beach environments.

Uses & applications

Extensively used as a building material, paving stone, decorative garden rock, and for carvings. Historically used in major architectural monuments and cathedrals.

Geological facts

The red color is caused by the presence of iron oxide coating the sand grains. Famous formations include the Antelope Canyon in Arizona and the red rocks of Sedona. It often preserves sedimentary structures like ripple marks or cross-bedding.

Field identification & locations

Identify in the field by its gritty, sandpaper-quality texture and visible layering (bedding). It will not fizz with HCl unless it has a calcitic cement. Found globally in basins across all geologic eras, notably the Old Red Sandstone of the Devonian period.