sedimentary

Ferruginous Sandstone

Arenite with Iron-Oxide cement (Fe2O3 · nH2O)

AI-generated identification · may be incorrect

Hardness: 6-7 on Mohs scale; Color: Greyish-blue with rusty orange/brown staining; Luster: Dull, earthy; Crystal structure: Granular/Clastic; Cleavage: None (conchoidal to irregular fracture).

Hardness: 6-7 on Mohs scale
Color: Greyish-blue with rusty orange/brown staining
Luster: Dull, earthy

Identified April 9, 2026More sedimentary →

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Physical properties

Hardness: 6-7 on Mohs scale; Color: Greyish-blue with rusty orange/brown staining; Luster: Dull, earthy; Crystal structure: Granular/Clastic; Cleavage: None (conchoidal to irregular fracture).

Formation & geological history

Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments. Often found in riverbeds or coastal environments where iron-rich groundwater precipitates oxides (like limonite or hematite) between grains.

Uses & applications

Used primarily as construction aggregate, building stone, or in landscaping. High-iron varieties were historically used as low-grade iron ore.

Geological facts

This specimen shows significant 'desert varnish' or oxidation staining. The pitting on the surface suggests chemical weathering where softer binder material has eroded out, leaving a more resistant silica/iron framework.

Field identification & locations

Identify by its gritty texture (feels like sandpaper) and distinct rust-colored staining. Common in sedimentary basins worldwide. For collectors, it represents the intersection of sedimentary geology and chemical weathering.