sedimentary
Red Sandstone
Arenite (with Iron Oxide / Hematite cementation)
Hardness: 6-7 Mohs (variable depending on cementation); Color: Rusty red, brown, or ochre; Luster: Dull/Earthy; Crystal Structure: Clastic (grain-based); Cleavage: None; Specific Gravity: 2.2-2.8
- Hardness
- 6-7 Mohs (variable depending on cementation)
- Color
- Rusty red, brown, or ochre
- Luster
- Dull/Earthy
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Physical properties
Hardness: 6-7 Mohs (variable depending on cementation); Color: Rusty red, brown, or ochre; Luster: Dull/Earthy; Crystal Structure: Clastic (grain-based); Cleavage: None; Specific Gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and litification of sand-sized mineral particles (mostly quartz and feldspar). The red color indicates formation in an oxygen-rich terrestrial environment where iron minerals oxidized. Commonly associated with desert dunes or river floodplains from the Paleozoic to Mesozoic eras.
Uses & applications
Widely used as a building material and decorative stone (brownstone), in paving, and as an abrasive in industrial applications. High-quality slabs are used for countertops and monuments.
Geological facts
Famous formations include the Red Rocks of Colorado and the 'Old Red Sandstone' of Great Britain. It is a primary reservoir rock for groundwater and petroleum because of its high porosity.
Field identification & locations
Identify in the field by its gritty, sandpaper-like texture and visible layering (bedding). It will not fizz with acid unless it contains calcite cement. Found globally in arid regions and prehistoric basins.
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