sedimentary
Red Sandstone
Arenite (with Iron Oxide / Hematite cementation)
Hardness: 6-7 on Mohs scale (due to quartz content); Color: Red, reddish-brown, or brick-red; Luster: Dull/Earthy; Crystal structure: Clastic (composed of sand-sized grains); Cleavage: None; Specific Gravity: 2.2-2.8
- Hardness
- 6-7 on Mohs scale (due to quartz content)
- Color
- Red, reddish-brown, or brick-red
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 on Mohs scale (due to quartz content); Color: Red, reddish-brown, or brick-red; Luster: Dull/Earthy; Crystal structure: Clastic (composed of sand-sized grains); Cleavage: None; Specific Gravity: 2.2-2.8
Formation & geological history
Formed by the accumulation and cementation of sand-sized minerals or rock grains. The red color suggests deposition in an oxygen-rich environment (terrestrial) where iron-bearing minerals oxidized into hematite. Often associated with ancient desert, river, or coastal environments.
Uses & applications
Commonly used in construction as a building stone (dimension stone), pavers, and decorative landscaping. High-quality varieties are used in historical architecture and monuments.
Geological facts
Famous for forming the 'Red Rocks' of the American Southwest. The red pigment is actually a very thin coating of iron oxide on the individual sand grains rather than the grains themselves being red.
Field identification & locations
Identify by its gritty, sandpaper-like texture and its visible sand grains. Found globally in continental sedimentary basins. Collectors look for unique 'Liesegang rings' or fossil inclusions within the layers.
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