sedimentary
Sandstone (Ferruginous)
Arenite with Hematite cement (SiO2 + Fe2O3)
Hardness: 6-7 (Mohs); Color: Reddish-brown, rust, or tan; Luster: Dull/Earthy; Crystal Structure: Clastic (granular); Cleavage: None; Specific Gravity: 2.2-2.8
- Hardness
- 6-7 (Mohs)
- Color
- Reddish-brown, rust, or tan
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: Reddish-brown, rust, or tan; Luster: Dull/Earthy; Crystal Structure: Clastic (granular); Cleavage: None; Specific Gravity: 2.2-2.8
Formation & geological history
Formed from the accumulation and lithification of sand-sized mineral grains or rock fragments. The reddish color indicates the presence of iron oxide (hematite) through oxidation of minerals in an oxygen-rich environment.
Uses & applications
Commonly used as a building material, paving stone, and in the production of glass (if high silica). Sometimes used for decorative landscaping.
Geological facts
Red sandstones are famous for forming dramatic landscapes like the Grand Canyon or the 'Red Rocks' of Sedona. They record ancient desert or river environments.
Field identification & locations
Identify by its gritty, sandpaper-like texture and visible sand grains. It is commonly found in sedimentary basins, riverbeds, and arid regions globally.
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