sedimentary
Ferruginous Sandstone
Sandstone (enriched with Iron Oxide)
Hardness: 6-7 (Mohs scale); Color: Brown, rusty orange, dark grey; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.2-2.8
- Hardness
- 6-7 (Mohs scale)
- Color
- Brown, rusty orange, dark grey
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Brown, rusty orange, dark grey; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments, with iron oxides (like hematite or goethite) acting as the binding cement. These typically form in river, desert, or marine environments over millions of years.
Uses & applications
Commonly used as a building material, in road construction, or as decorative garden stones. High-iron variants were historically used as low-grade iron ore.
Geological facts
The reddish-brown staining is caused by the oxidation of iron minerals, essentially the same process that causes rust. This stone is often associated with 'ironstones' and can sometimes preserve trace fossils or burrows.
Field identification & locations
Identify in the field by its gritty texture (feels like sandpaper) and its characteristic rusty color. It is extremely common in sedimentary basins worldwide. For collectors, it is usually valued for its texture or specific localities.
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