sedimentary

Ferruginous Sandstone

Arenite with Iron-Oxide cement (primarily Fe2O3 • nH2O)

Hardness: 6-7 (Mohs); Color: Reddish-brown, orange, or rust-colored due to iron oxidation; Luster: Dull to earthy; Structure: Clastic, fine to medium-grained; Cleavage: None; Specific Gravity: 2.2 - 2.8

Hardness: 6-7 (Mohs)
Color: Reddish-brown, orange, or rust-colored due to iron oxidation
Luster: Dull to earthy

Identified March 8, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation of sand-sized mineral particles or rock fragments, which are then cemented together by iron oxides (like limonite or hematite) leaching from groundwater in terrestrial or shallow marine environments.

Uses & applications

Commonly used as building stone, fill material in construction, and occasionally as a source of iron ore if the concentration is high enough. Small pieces are often kept as educational geological specimens.

Geological facts

The distinct red-orange coloring is essentially 'stone rust.' This type of rock is responsible for the iconic landscapes of the American Southwest, such as the Red Rocks of Sedona and the Arches National Park.

Field identification & locations

Identify in the field by its gritty 'sandpaper' texture and the characteristic orange-red staining that often rubs off slightly on the skin. It is frequently found in desert regions, riverbeds, and exposed canyon walls.

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