sedimentary
Red Sandstone
Arenite (primarily Quartz, SiO2, with Iron Oxide/Hematite)
Hardness: 6-7 (individual grains); Color: Red, reddish-brown, or orange; Luster: Dull/Earthy; Structure: Clastic, fine-to-medium grained; Specific Gravity: 2.2-2.8
- Hardness
- 6-7 (individual grains)
- Color
- Red, reddish-brown, or orange
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (individual grains); Color: Red, reddish-brown, or orange; Luster: Dull/Earthy; Structure: Clastic, fine-to-medium grained; Specific Gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and cementation of sand-sized grains, typically in desert or river environments. The red color suggests deposition in an oxygen-rich environment (subaerial) where iron minerals oxidized into hematite.
Uses & applications
Used extensively in construction as dimension stone, paving, and decorative garden landscaping. Historical use in cathedrals and monuments.
Geological facts
Famous red sandstone formations include the Grand Canyon, Sedona's rocks in Arizona, and the 'Old Red Sandstone' found in the UK, which was pivotal in early geological dating.
Field identification & locations
Identify by its gritty feel (like sandpaper) and visible layering/bedding. It will not fizz with acid unless it has a calcitic cement. Found globally in ancient basins.
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