sedimentary
Red Sandstone
Arenite (primarily Quartz with Hematite cement)
Hardness: 6-7 (on Mohs scale); Color: Red, reddish-brown, or pinkish; Luster: Dull or earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.2-2.8
- Hardness
- 6-7 (on Mohs scale)
- Color
- Red, reddish-brown, or pinkish
- Luster
- Dull or earthy
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Physical properties
Hardness: 6-7 (on Mohs scale); Color: Red, reddish-brown, or pinkish; Luster: Dull or earthy; Crystal structure: Granular/Clastic; Cleavage: None; Specific gravity: 2.2-2.8
Formation & geological history
Formed through the accumulation and cementation of sand-sized mineral grains or rock fragments. The red color is typically derived from the presence of iron oxide (hematite) which acts as a cementing agent. These deposits often form in desert or fluvial (river) environments over millions of years.
Uses & applications
Commonly used as a building material, paving stone, and in decorative landscaping. It is also used as an abrasive in industrial processes and for manufacturing glass when quartz content is high.
Geological facts
Many of the world's most famous geological landmarks, such as the Grand Canyon in the USA and Petra in Jordan, are primarily composed of various layers of red sandstone. It is often referred to as 'Old Red Sandstone' in British geology.
Field identification & locations
Identify in the field by its distinctive gritty, sandpaper-like feel and visible grains. It can be found globally, particularly in arid regions or uplifted mountain ranges. Collectors look for unique banding or fossil inclusions.
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