sedimentary
Red Sandstone
Arenite (primarily Quartz and Feldspar with Iron Oxide cement)
Hardness: 6-7 (individual grains); Color: Red, reddish-brown, or rust-colored; Luster: Dull or earthy; Crystal structure: Clastic (typically fine to medium grains); Cleavage: None; Specific gravity: 2.2-2.8
- Hardness
- 6-7 (individual grains)
- Color
- Red, reddish-brown, or rust-colored
- Luster
- Dull or earthy
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Physical properties
Hardness: 6-7 (individual grains); Color: Red, reddish-brown, or rust-colored; Luster: Dull or earthy; Crystal structure: Clastic (typically fine to medium grains); Cleavage: None; Specific gravity: 2.2-2.8
Formation & geological history
Formed through the lithification of sand-sized particles (0.0625 to 2 mm). The distinctive red color is caused by the oxidation of iron minerals (hematite) during the depositional process, common in arid, terrestrial, or shallow-marine environments. Many deposits range from 200 to 500 million years old (Paleozoic to Mesozoic era).
Uses & applications
Used extensively as dimensional stone for cathedral and building construction, paving stones, aggregate in concrete, and for decorative gardening and masonry.
Geological facts
Red sandstone formed the iconic 'Red Rocks' of Colorado and the Grand Canyon strata. It was a preferred building material in the 19th century and is often associated with the 'Old Red Sandstone' formations found in Scotland which helped James Hutton develop the theory of uniformitarianism.
Field identification & locations
Identify in the field by its gritty texture (feels like sandpaper) and distinct bedding planes. It is commonly found in the Southwestern United States, parts of Northern England, and Central Australia. Collectors should look for unique cross-bedding patterns or ripple marks within the layers.
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