sedimentary
Red Sandstone
Ferruginous Sandstone (formula varies, primarily SiO2 with Fe2O3)
Hardness: 6-7 on Mohs scale; Color: Reddish-brown to brick red; Luster: Dull or earthy; Crystal structure: Clastic texture with sand-sized grains; Cleavage: None; Specific gravity: 2.2 to 2.8.
- Hardness
- 6-7 on Mohs scale
- Color
- Reddish-brown to brick red
- Luster
- Dull or earthy
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Physical properties
Hardness: 6-7 on Mohs scale; Color: Reddish-brown to brick red; Luster: Dull or earthy; Crystal structure: Clastic texture with sand-sized grains; Cleavage: None; Specific gravity: 2.2 to 2.8.
Formation & geological history
Formed by the accumulation and cementation of sand-sized grains of mineral or rock fragments. The red color is due to the presence of iron oxides (hematite) during the lithification process, often in arid or continental environments.
Uses & applications
Widely used as a construction material for building facades, paving, and monuments. It is also popular in landscaping and as a decorative stone.
Geological facts
Red sandstone is famous for creating iconic geological features like the Red Rocks Amphitheatre in Colorado and the 'Old Red Sandstone' formations in Great Britain which helped James Hutton develop the theory of uniformitarianism.
Field identification & locations
Identify by its gritty texture (feels like sandpaper) and distinct red/brown staining that does not wash off. Found in desert environments or ancient river beds. Collectors look for unique banding or fossil inclusions.
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