sedimentary
Red Sandstone (Iron-rich Sandstone)
Clastic Sedimentary Rock - Quartz Arenite / Arkose with Hematite Cement
Hardness: 6-7 (Mohs scale for individual grains); Color: Red, reddish-brown, or rust-orange; Luster: Dull or earthy; Crystal structure: Amorphous/Granular (clastic texture); Specific gravity: 2.2-2.8
- Hardness
- 6-7 (Mohs scale for individual grains)
- Color
- Red, reddish-brown, or rust-orange
- Luster
- Dull or earthy
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Physical properties
Hardness: 6-7 (Mohs scale for individual grains); Color: Red, reddish-brown, or rust-orange; Luster: Dull or earthy; Crystal structure: Amorphous/Granular (clastic texture); Specific gravity: 2.2-2.8
Formation & geological history
Formed by the accumulation of sand-sized mineral particles or rock fragments, subsequently cemented by iron oxides (hematite) in terrestrial environments like deserts (aeolian) or riverbeds (fluvial). Ages vary widely from Precambrian to Cenozoic.
Uses & applications
Used extensively as a building material, landscape stone, and for paving. Historically significant in masonry and architectural facades (e.g., 'Brownstone' or 'Red Sandstone' cathedrals).
Geological facts
The distinct red color is due to the oxidation of iron minerals, essentially making the rock 'rusted.' Most 'Red Beds' were formed during the Permian and Triassic periods when large landmasses were arid.
Field identification & locations
Identify in the field by its gritty, sandpaper-like texture and its tendency to rub off a reddish dust or show visible layers (bedding). Commonly found in the American Southwest (Grand Canyon), Scotland, and central India. Collectors look for unique banding or fossils.
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