sedimentary
Red Sandstone
Clastic Terrigenous Sedimentary Rock (composed mostly of SiO2 with Fe2O3)
Hardness: 6-7 (Mohs scale) if quartz-rich; Color: reddish-brown to terracotta; Luster: dull to earthy; Structure: granular, clastic; Cleavage: none; Specific gravity: approx. 2.2-2.8.
- Hardness
- 6-7 (Mohs scale) if quartz-rich
- Color
- reddish-brown to terracotta
- Luster
- dull to earthy
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Physical properties
Hardness: 6-7 (Mohs scale) if quartz-rich; Color: reddish-brown to terracotta; Luster: dull to earthy; Structure: granular, clastic; Cleavage: none; Specific gravity: approx. 2.2-2.8.
Formation & geological history
Formed by the accumulation of sand-sized mineral grains and rock fragments, cemented together over millions of years by minerals like silica or iron oxide. The red color suggests deposition in highly oxidizing continental environments such as deserts or river floodplains.
Uses & applications
Used extensively as a building stone (brownstone), in paving, landscaping, and as a source of industrial sand for glassmaking and fracking. Also valued as an ornamental stone.
Geological facts
Red sandstone is a key component of iconic geological formations like the Grand Canyon and the Red Rocks of Sedona. The red hue comes from hematite (iron oxide) coating the individual grains.
Field identification & locations
Identify in the field by its gritty texture and visible sand grains. It is commonly found in ancient basins and arid regions globally. Its durability and ease of carving make it a favorite for architectural masonry.
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