sedimentary
Red Sandstone
Clastic Terrigenous Sedimentary Rock (primarily SiO2 with Fe2O3 coating)
Hardness: 6-7 on Mohs scale (due to quartz content); Color: Red, reddish-brown, or brick-red; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.2-2.8
- Hardness
- 6-7 on Mohs scale (due to quartz content)
- Color
- Red, reddish-brown, or brick-red
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 on Mohs scale (due to quartz content); Color: Red, reddish-brown, or brick-red; Luster: Dull/Earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and lithification of sand-sized mineral grains (mostly quartz) in arid desert environments or river basins. The red color comes from iron oxide (hematite) coating the grains, often dating from the Paleozoic or Mesozoic eras.
Uses & applications
Extensively used as a building material, masonry, paving stones, and in abrasive manufacturing. Highly valued as a decorative stone in landscaping and for crushed stone in construction.
Geological facts
Famous structures like the 'Red City' of Petra in Jordan and many iconic American Southwest formations (like the Grand Canyon or Sedona) are composed of various red sandstones. It is often referred to as 'Old Red Sandstone' in a historical geological context.
Field identification & locations
Identify in the field by its gritty 'sandpaper' feel and visible layers (bedding). It is commonly found in the Colorado Plateau (USA), Scotland, and central Australia. To distinguish it from shale, note its coarser texture and lack of easy splitting into thin plates.
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