sedimentary
Red Sandstone
Arenite (composed primarily of Quartz and Iron Oxide)
Hardness: 6.5-7 (based on quartz content); Color: Red, reddish-brown, or orange due to hematite; Luster: Dull/Earthy; Crystal structure: Clastic (grainy); Cleavage: None; Specific Gravity: 2.2-2.8
- Hardness
- 6
- Color
- Red, reddish-brown, or orange due to hematite
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6.5-7 (based on quartz content); Color: Red, reddish-brown, or orange due to hematite; Luster: Dull/Earthy; Crystal structure: Clastic (grainy); 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 red color suggests deposition in an oxygen-rich environment (arid or terrestrial) where iron minerals oxidized. Common in Mesozoic and Paleozoic formations.
Uses & applications
Extensively used as a building material, decorative stone in masonry, paving, and occasionally for grindstones or filter media.
Geological facts
Famous structures built from red sandstone include the Red Fort in Delhi and the ancient city of Petra. The 'Old Red Sandstone' is a famous geological sequence in Britain that helped pioneers of geology understand Earth's history.
Field identification & locations
Identify by its gritty, sandpaper-like texture and its layering (bedding planes). Found globally in sedimentary basins. Collectors often look for examples with unique ripple marks or cross-bedding.
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