sedimentary
Red Sandstone
Ferruginous Sandstone (SiO2 with Fe2O3)
Hardness: 6-7 (Mohs); Color: terracotta, red, or reddish-brown; Luster: dull to earthy; Structure: clastic; Cleavage: none; Texture: gritty, like sandpaper.
- Hardness
- 6-7 (Mohs)
- Color
- terracotta, red, or reddish-brown
- Luster
- dull to earthy
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Physical properties
Hardness: 6-7 (Mohs); Color: terracotta, red, or reddish-brown; Luster: dull to earthy; Structure: clastic; Cleavage: none; Texture: gritty, like sandpaper.
Formation & geological history
Formed by the accumulation of sand-sized mineral grains or rock fragments, cemented together by silica, calcium carbonate, or iron oxide. The red color indicates formation in an oxygen-rich environment where iron minerals oxidized.
Uses & applications
Commonly used as a building material for facades, pavers, and retaining walls; also popular for decorative landscaping and as an abrasive in industrial applications.
Geological facts
Red sandstone formations, such as the Old Red Sandstone, are famous for preserving early vertebrate fossils. It is the primary material used in the construction of iconic structures like the Red Fort in India and Petra in Jordan.
Field identification & locations
Identified by its gritty texture and distinct layering or cross-bedding. In the field, look for consistent grain sizes and the ability to rub small grains of sand off the surface with a finger.
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