sedimentary

Ferruginous Sandstone

Sandstone (rich in iron oxides/hydroxides)

Hardness: 6-7 (approx); Color: Dark brown, reddish-brown, or rust-colored; Luster: Dull or earthy; Crystal Structure: Clastic grains cemented by iron minerals; Cleavage: None; Specific Gravity: Approx 2.3-2.6

Hardness: 6-7 (approx)
Color: Dark brown, reddish-brown, or rust-colored
Luster: Dull or earthy

Identified April 12, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments, with iron-rich fluids (like groundwater containing hematite or goethite) acting as the cementing agent. These specifically form in oxidising environments.

Uses & applications

Commonly used as a building stone or road aggregate. Some high-iron versions (ironstone) have historically been mined as iron ore.

Geological facts

Ferruginous sandstones are responsible for the dramatic red and brown colors of the American Southwest. The 'rust' on the grains is often just a thin coating that gives the entire rock its color.

Field identification & locations

Identify by its gritty texture (feels like sandpaper) and dark brown/red color that doesn't wash off. It will often leave a reddish-brown streak if scraped against unglazed porcelain. Commonly found in riverbeds or eroded sedimentary plateaus.

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