sedimentary
Sandstone (Ferruginous)
Arenite with Iron Oxide cement
Hardness: 6-7 on Mohs scale; Color: Reddish-brown, tan, or rusty due to iron oxidation; Luster: Dull or earthy; Crystal structure: Granular (clastic texture); Cleavage: None; Specific gravity: 2.2 - 2.8
- Hardness
- 6-7 on Mohs scale
- Color
- Reddish-brown, tan, or rusty due to iron oxidation
- Luster
- Dull or earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Reddish-brown, tan, or rusty due to iron oxidation; Luster: Dull or earthy; Crystal structure: Granular (clastic texture); 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. The reddish hue indicates an oxygen-rich environment during deposition or later weathering where iron minerals like hematite or goethite acted as the cementing agent. Most common in terrestrial or shallow marine environments.
Uses & applications
Used primarily as construction material, paving stone, road aggregate, and historically for building monuments. Fine-grained variants are sometimes used for sharpening tools (whetstones).
Geological facts
Sandstone contains about 20-25% of all sedimentary rocks in the Earth's crust. It is a major reservoir for groundwater, oil, and natural gas due to its porosity and permeability. The Grand Canyon's famous red layers are largely composed of various ferruginous sandstones.
Field identification & locations
Identify in the field by its 'sandpaper' feel when rubbed. It should leave a gritty residue. Often found in layered outcrops, riverbeds, and deserts. Collectors look for unique banding or fossil inclusions.
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