sedimentary
Red Sandstone
Arenite (ferruginous sandstone)
Hardness: 6-7 (Mohs scale); Color: Red, reddish-brown, or rust; Luster: Dull/Earthy; Crystal structure: Clastic (predominantly quartz grains); Cleavage: None (breaks across grains); Specific gravity: 2.2–2.8
- Hardness
- 6-7 (Mohs scale)
- Color
- Red, reddish-brown, or rust
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 (Mohs scale); Color: Red, reddish-brown, or rust; Luster: Dull/Earthy; Crystal structure: Clastic (predominantly quartz grains); Cleavage: None (breaks across grains); Specific gravity: 2.2–2.8
Formation & geological history
Formed through the accumulation and lithification of sand-sized mineral particles or rock fragments. The red color indicates formation in an oxygen-rich terrestrial environment (arid or desert) where iron minerals oxidize (rust) to coat the sand grains. Common in formations spanning from the Precambrian to the Cenozoic.
Uses & applications
Historically used as a common building material and for stone masonry (e.g., Brownstones). In industry, high-silica sandstone is used for glass manufacturing and as an abrasive. Crushed sandstone is used in road construction and as concrete aggregate.
Geological facts
Red sandstone is famous for creating the dramatic landscapes of the American Southwest, such as the Grand Canyon, Sedona, and Arches National Park. It often contains cross-bedding structures that reveal ancient wind or water current directions.
Field identification & locations
Identify in the field by a gritty, sandpaper-like feel and the presence of visible sand grains. It is commonly found in 'red beds' worldwide, including the Colorado Plateau and Northern England. Collectors look for pieces with unique patterns or dinosaur track fossil inclusions.
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