sedimentary
Ferruginous Sandstone
Arenite with Iron-Oxide Cement
Hardness: 6-7 (Mohs). Color: Tan, brown, or dark red/orange due to iron oxidation. Luster: Dull to earthy. Structure: Granular/clastic. Cleavage: None.
- Hardness
- 6-7 (Mohs)
- Color
- Tan, brown, or dark red/orange due to iron oxidation
- Luster
- Dull to earthy
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Physical properties
Hardness: 6-7 (Mohs). Color: Tan, brown, or dark red/orange due to iron oxidation. Luster: Dull to earthy. Structure: Granular/clastic. Cleavage: None.
Formation & geological history
Formed through the lithification of sand grains where iron minerals (like hematite or goethite) act as the binding cement. Commonly found in terrestrial or shallow marine environments with fluctuating water tables.
Uses & applications
Used primarily as low-grade building stone, road fill, and sometimes as a minor source of iron ore if the concentration is high enough.
Geological facts
This rock's distinct reddish-orange staining is essentially 'rock rust'. In many arid regions, it forms a resistant layer known as a 'duricrust' that protects the ground from erosion.
Field identification & locations
Identify by its gritty, sand-paper like feel and the presence of reddish-orange oxidation patches on a tan or grey matrix. Commonly found in desert mesas or riverbeds.
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