sedimentary
Red Sandstone
Clastic sedimentary rock (primarily Quartz and Feldspar with Iron Oxide cement)
Hardness: 6-7 on Mohs scale; Color: Reddish-brown, rust, or clay-like hues; Luster: Dull to earthy; Crystal structure: Granular/clastic; Cleavage: None; Specific gravity: 2.2-2.8.
- Hardness
- 6-7 on Mohs scale
- Color
- Reddish-brown, rust, or clay-like hues
- Luster
- Dull to earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Reddish-brown, rust, or clay-like hues; Luster: Dull to earthy; Crystal structure: Granular/clastic; Cleavage: None; Specific gravity: 2.2-2.8.
Formation & geological history
Formed through the accumulation of sand-sized mineral particles or rock fragments, subsequently cemented by iron oxides (hematite) typically in arid, continental, or river-delta environments. Most prominent deposits date to the Devonian and Triassic periods.
Uses & applications
Used extensively as a building material, decorative stone, masonry, and for paving. Historically utilized in the construction of cathedrals and monuments.
Geological facts
The 'Old Red Sandstone' of Europe was once used as a key piece of evidence by James Hutton to establish the concept of deep geological time. Its signature red color is the result of chemical weathering involving iron minerals.
Field identification & locations
Identify in the field by its gritty texture (feels like sandpaper) and distinct reddish staining that does not wash off. Found globally, with famous deposits in the Southwestern USA, Scotland, and India. Collectors look for unique layering or cross-bedding patterns.
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