sedimentary
Red Sandstone
Clastic sedimentary rock (primarily SiO2 with Fe2O3 iron oxide staining)
Hardness: 6-7 (Mohs scale); Color: Brick red to brownish-red; Luster: Dull/Earthy; Crystal Structure: Microcrystalline matrix with visible sand grains; Cleavage: None (granular); Specific Gravity: 2.2–2.8
- Hardness
- 6-7 (Mohs scale)
- Color
- Brick red to brownish-red
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Brick red to brownish-red; Luster: Dull/Earthy; Crystal Structure: Microcrystalline matrix with visible sand grains; Cleavage: None (granular); Specific Gravity: 2.2–2.8
Formation & geological history
Formed by the accumulation of sand-sized mineral grains or rock fragments, cemented together over millions of years by minerals like silica, calcite, or iron oxide. The red color is typically due to hematite staining in arid, terrestrial environments.
Uses & applications
Extensively used in construction for building facades, paving, and monuments. It is also used in crushed form as road base or landscaping material. Finely textured pieces are popular for ornamental carvings.
Geological facts
The famous 'Red Rocks' of Colorado and the 'Old Red Sandstone' of Great Britain are classic geological formations. Its color serves as a 'paleoclimate' indicator, suggesting the rock formed in an environment with high oxygen and seasonal wetting/drying.
Field identification & locations
Identify in the field by its gritty 'sandpaper' texture and the presence of visible layers (bedding). Rubbing two pieces together will usually release small grains of sand. Common in the Southwestern United States, Northern England, and Central Australia.
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